UNIVERSIDAD NACIONAL AUTÓNOMA DE MÉXICO POSGRADO EN CIENCIAS BIOLÓGICAS INSTITUTO DE ECOLOGÍA ECOLOGÍA CARACTERIZACIÓN FUNCIONAL Y ECOLÓGICA DEL MAÍZ MEJÉN EN COMALCALCO, TABASCO TESIS QUE PARA OPTAR POR EL GRADO DE: DOCTOR EN CIENCIAS PRESENTA: HUMBERTO PERAZA VILLARREAL TUTORA PRINCIPAL DE TESIS: DRA. ALMA DELFINA LUCÍA OROZCO SEGOVIA INSTITUTO DE ECOLOGÍA, UNAM COMITÉ TUTOR: DR. ALEJANDRO CASAS FERNÁNDEZ INSTITUTO DE INVESTIGACIONES EN ECOSISTEMAS Y SUSTENTABILIDAD, UNAM DR. ROBERTO ANTONIO LINDIG CISNEROS INSTITUTO DE INVESTIGACIONES EN ECOSISTEMAS Y SUSTENTABILIDAD, UNAM CIUDAD UNIVERSITARIA, CIUDAD DE MÉXICO, NOVIEMBRE 2023 UNAM – Dirección General de Bibliotecas Tesis Digitales Restricciones de uso DERECHOS RESERVADOS © PROHIBIDA SU REPRODUCCIÓN TOTAL O PARCIAL Todo el material contenido en esta tesis esta protegido por la Ley Federal del Derecho de Autor (LFDA) de los Estados Unidos Mexicanos (México). El uso de imágenes, fragmentos de videos, y demás material que sea objeto de protección de los derechos de autor, será exclusivamente para fines educativos e informativos y deberá citar la fuente donde la obtuvo mencionando el autor o autores. Cualquier uso distinto como el lucro, reproducción, edición o modificación, será perseguido y sancionado por el respectivo titular de los Derechos de Autor. UNIVERSIDAD NACIONAL AUTÓNOMA DE MÉXICO POSGRADO EN CIENCIAS BIOLÓGICAS INSTITUTO DE ECOLOGÍA ECOLOGÍA CARACTERIZACIÓN FUNCIONAL Y ECOLÓGICA DEL MAÍZ MEJÉN EN COMALCALCO, TABASCO TESIS QUE PARA OPTAR POR EL GRADO DE: DOCTOR EN CIENCIAS PRESENTA: HUMBERTO PERAZA VILLARREAL TUTORA PRINCIPAL DE TESIS: DRA. ALMA DELFINA LUCÍA OROZCO SEGOVIA INSTITUTO DE ECOLOGÍA, UNAM COMITÉ TUTOR: DR. ALEJANDRO CASAS FERNÁNDEZ INSTITUTO DE INVESTIGACIONES EN ECOSISTEMAS Y SUSTENTABILIDAD, UNAM DR. ROBERTO ANTONIO LINDIG CISNEROS INSTITUTO DE INVESTIGACIONES EN ECOSISTEMAS Y SUSTENTABILIDAD, UNAM CIUDAD UNIVERSITARIA, CIUDAD DE MÉXICO, NOVIEMBRE 2023 COORDINACIÓN GENERAL DE ESTUDIOS DE POSGRADO COORDINACIÓN DEL POSGRADO EN CIENCIAS BIOLÓGICAS ENTIDAD INSTITUTO DE ECOLOGÍA OFICIO: CGEP/CPCB/IE/0637/2023 ASUNTO: Oficio de Jurado M. en C. Ivonne Ramírez Wence Directora General de Administración Escolar, UNAM P r e s e n t e Me permito informar a usted, que el Comité Académico, del Posgrado en Ciencias Biológicas, en su reunión ordinaria del día 8 de mayo de 2023 se aprobó el siguiente jurado para el examen de grado de DOCTOR EN CIENCIAS del estudiante PERAZA VILLARREAL HUMBERTO con número de cuenta 301748528 con la tesis titulada “examen para obtener el de grado de DOCTOR EN CIENCIAS, con la tesis titulada: “CARACTERIZACIÓN FUNCIONAL Y ECOLÓGICA DEL MAÍZ MEJÉN EN COMALCALCO, TABASCO”. Bajo la dirección de la DRA. ALMA DELFINA LUCIA OROZCO SEGOVIA, Tutora Principal, quedando integrado de la siguiente manera: Presidente: DRA. JULIETA ALEJANDRA ROSELL GARCÍA Vocal: DRA. ANA ISABEL MORENO CALLES Secretario: DR. ALEJANDRO CASAS FERNÁNDEZ Vocal: DRA. MARIANA BENÍTEZ KEINRAD Vocal: DR. ROBERTO ANTONIO LINDIG CISNEROS Sin otro particular, me es grato enviarle un cordial saludo. A T E N T A M E N T E “POR MI RAZA HABLARÁ EL ESPÍRITU” Ciudad Universitaria, Cd. Mx., a 21 de agosto de 2023 COORDINADOR DEL PROGRAMA c. c. p. Expediente del alumno AGNS/ERR/EARR/err AGRADECIMIENTOS INSTITUCIONALES Al Posgrado en Ciencias Biológicas de la Universidad Nacional Autónoma de México, por el apoyo en mi formación como Doctor en Ciencias. Al Consejo Nacional de Humanidades, Ciencias y Tecnologías por brindarme una beca para llevar a cabo mis estudios de doctorado (número de beca 334495). A la DGAPA-PAPIIT IN-205715 y el proyecto SEP-CONACyT-221015 por el financiamiento de este proyecto. Al Instituto de Ecología por permitirme usar sus instalaciones para desarrollo del proyecto. A mi tutora, la Dra. Alma Delfina Lucía Orozco Segovia por brindarme su ejemplo, por su apoyo y consejos. A mi Comité Tutor: Dr. Alejandro Casas Fernández y Dr. Roberto Lindig Cisneros por darle seguimiento a mi trabajo y por sus consejos y observaciones para mejorar mi tesis. AGRADECIMIENTOS PERSONALES Agradezco al Dador de Vida, por permitirme disfrutar lo bello de la naturaleza. A la Dra. Alma Orozco Segovia por su confianza, paciencia, comprensión y apoyo, en cada uno de los momentos del desarrollo de este proyecto. Muchas gracias por compartirme sus condimentos y amor por los pantanos de Tabasco. Agradezco a los miembros del jurado conformado por la Dra. Mariana Benítez Keinrad, Dra. Julieta Alejandra Rosell García, Dra. Ana Isabel Moreno Calles, Dr. Alejandro Casas Fernández y Dr. Roberto Lindig Cisneros, por la revisión, comentarios y sugerencias al escrito de la tesis. Todas sus observaciones realizadas fueron muy valiosas para mejorar y poder concluir el trabajo de escritura. A M. en C. María Esther Sánchez Coronado, a la Dra. Rosa Jimena Rey Loaiza, a el Dr. José Gerardo Rodríguez Tapia, al M. en I. Alejandro René González Ponce y al M. en I. José Miguel Baltazar Gálvez; por el soporte técnico. Agradezco a las y los agricultores de Comalcalco, Cunduacán, Jonuta, Jalpa de Méndez, Nacajuca y Centla, quienes siempre me recibieron con calidez en sus hogares, parcelas y pantanos. En especial, agradezco a Doña Yara Alcudia Candelero por todo el apoyo, la orientación y las pláticas tan valiosas, las cuales me permitieron comprender un poco más sobre el agroecosistema marceño y la importancia del maíz mején para su comunidad. Agradezco a Don Arnulfo, Daniel Córdova, Don Livio Córdoba y Don Isaías por su amabilidad, por todo su apoyo en campo. A mis padres que siempre me han apoyado a lo largo de mi vida y a los cuales amo. A Luz Palestina por todos esos consejos en los momentos críticos, por la comprensión y ser un ser de luz y de inspiración. Agradezco a la familia Llamas Guzmán por todo el apoyo recibido. Agradezco a mis compañeros del laboratorio fisiología vegetal. A la Mtra. María Esther Sánchez Coronado por su amistad, apoyo y todos los consejos compartidos. Agradezco Erika Rodríguez Reyes por su amistad y su gran apoyo en todos los procesos de posgrados. ÍNDICE RESUMEN …………………………………………........……………………………........ 1 ABSTRACT …………………………………………………………….............................. 3 INTRODUCCIÓN GENERAL………………………………………………………........ 5 Caracterización funcional y ecología del maíz mején en Comalcalco, Tabasco.............. 5 Grupos culturales, agroecosistemas y agrobiodiversidad en México ……......…........ 5 Centro de origen, domesticación y diversificación del maíz…….......……………….. 6 La resiliencia de los agroecosistemas ante el cambio climático global………........... 7 El maíz nativo mején y el agroecosistema marceño……..................………….......…. 11 El agroecosistema marceño en Tabasco: pasado y presente ……………......………. 13 Cambios sociales, ecológicos y políticos que incidieron en la dinámica hidrológica de la planicie aluvial de Tabasco y en la agricultura……..................,…................…. 17 El marceño como una alternativa para la transición agroecológica ………….......…. 19 Preguntas de investigación...................................................................……………...…. 20 Hipótesis general...............................................................................………………...…. 21 Objetivo general............................................................................…………………...…. 22 Objetivo particulares....................................................................…………………...…. 22 Literatura Citada…........................................................................................................... 23 CAPÍTULO I (ARTÍCULO DE REQUISITO) THE MARCEÑO AGROECOSYSTEM: TRADITIONAL MAIZE PRODUCTION AND WETLAND MANAGEMENT IN TABASCO, MEXICO…………...............................…. 38 CAPÍTULO II HUMAN LIVELIHOODS AND WETLANDS CONSERVATION IMPROVED FOR THE TRADITIONAL MANAGEMENT AND USE OF THE MEJÉN MAIZE IN THE MARCEÑO AGROECOSYSTEM, IN TABASCO, MÉXICO.....…………....................................................................................................…… 57 DISCUSIÓN GENERAL……………….........…………….................................………… 144 Importancia de los humedales en la seguridad alimentaria y los agroecosistemas tradicionales……………..........……….....................................................…........................ 144 Diversidad del maíz nativo mején…………………………………..………..........……… 150 CONCLUSIÓN………………………………………......….........……............................... 153 Literatura citada……………………………..………………………………………… 155 RESUMEN Los agroecosistemas milperos se han adaptado a una gran diversidad de ecosistemas presentes en el territorio mexicano, lo que representa el conjunto de conocimientos y saberes bioculturales generados por los diversos grupos indígenas y mestizos de México. Dichos conocimientos son reflejados en las prácticas de la agricultura tradicional que han permitido adaptar y conservar in situ la enorme diversidad de maíces nativos. El 65% de la producción de maíz en México se cultiva bajo condiciones de temporal. Existe un riesgo considerable debido al aumento previsto de las temperaturas, la disminución de la precipitación y el aumento de los fenómenos meteorológicos extremos relacionados con el cambio climático. Lo anterior generará un impacto significativo en la producción agrícola lo que representa una de las mayores amenazas para la seguridad alimentaria mundial. Los agroecosistemas tradicionales representan un estratégico reservorio genético y de conocimientos que permitirán la generación de variedades de cultivos y estrategias de sistemas alimentarios resilientes, adaptados a las nuevas condiciones ambientales que se presenten en el contexto del cambio climático global, en el cual el agroecosistema marceño que se práctica en la planicie aluvial de Tabasco. En el primer capítulo se describe la distribución del agroecosistema marceño con base al relieve del terreno. Se encontró que en la actualidad se practica en 203 comunidades rurales mayas chontales y mestizas. Por medio de sistemas de información geográfica (SIG), variables bioclimáticas y de modelos de distribución potencial de 16 especies de plantas silvestres asociadas al agroecosistema marceño se estimaron las áreas actualmente usadas para actividades agrícolas y ganaderas con inundaciones cíclicas las cuales tienen potencial de reconvertirse al agroecosistema marceño, como una estrategia productiva de adaptación al cambio climático. Para estimar esta información se generó un modelo de probabilidad de ocurrencia del marceño a través de MaxEnt, el cual fue superpuesto a un modelo de elevación del terreno (LiDAR) geoprocesado con SIG. Los resultados obtenidos en este capítulo muestran que el agroecosistema marceño es una práctica vigente y está presente en 203 localidades en ocho municipios de Tabasco y se estimó que este tipo de agricultura tradicional es practicada en alrededor del 2% del área estatal, en elevaciones de 1 a 7 metros. Estimamos que la superficie con potencial de reconversión al sistema marceño es de alrededor del 18.4% del área estatal. Se propone la implementación de este agroecosistema en un área más amplia, como una alternativa para desarrollo de la agricultura y la autosuficiencia alimentaria local y una estrategia para la restauración ecológica y de los servicios ecosistémicos de los humedales, así como para la conservación del paisaje biocultural de las tierras bajas de Tabasco. En el segundo capítulo, se caracterizaron las labores culturales actuales de manejo del agreoecosistema marceño, en la vegetación de popales, el cual se practica durante la estación seca del año (de marzo a junio) con la siembra de la variedad de maíz nativo 1 llamado mején, al inicio de su cultivo en los pantanos, el “popal” es cortado e incorporado a los suelos fértiles y húmedos como abono, lo que puede mejorar sus propiedades físico- químicas, lo que permite en las parcelas inundables (15– 30 días de inundación) y de pantano (6–8 meses de inundación), ser altamente productivas, ya que en el presente trabajo se estimó una densidades de siembra de 34,339 a 47,4004 plantas ha–1 que produjo un rendimiento de 3.3 Mg ha–1 de grano de maíz nativo mején, a muy bajo costo ($94.75 a $246.28 USD ha−1) y con un reducido uso de insumos externos al sistema. Los principales atributos de selección de la semilla y la predilección de la variedad nativa de maíz mején, en la región son ocho características: el sabor de la masa, el rendimiento de la mazorca, la altura de la mazorca con respecto al suelo, la facilidad de desgranar, el sabor del grano en los alimentos y el diámetro del olote. Asimismo, se realizó una caracterización morfológica de las mazorcas y plantas del maíz nativo mején. Con base en datos morfológicos de 36 accesiones de mazorcas identificamos que el agroecosistema mantuvo una importante diversidad del maíz nativo mején. Una de las características morfológicas relevantes de la planta de este maíz es la altura de la mazorca en la planta (1 .88 ± 0.20 m), que permite al agricultor realizar la dobla de la caña de maíz por debajo de la mazorca para iniciar el secado de ésta sin que tenga contacto con el espejo de agua durante las inundaciones y la mazorca puede ser cosechada en presencia de ésta. Finalmente, este trabajo muestra la composición florística asociada a las inundaciones del pantano y el agroecosistema marceño, se enlistan 144 especies de hidrófitas y plantas tolerantes a la inundación, asociadas a este sistema agrícola, lo que permite hablar de la resiliencia del manejo actual del agroecosistema y los valores culturales relacionados con este sistema agrícola, así como la conservación in situ de la variedad de maíz nativo mején por agricultores que mantienen vivo el conocimiento tradicional del manejo de popales en las zonas pantanosas de Tabasco. Este agroecosistema de origen prehispánico permite que la cosecha se realice a pie, en canoas o a caballo durante la época de lluvias y que a pesar de que el manejo de los pantanos con este agroecosistema decayó en la década de 90´s, cuando se aplicó el Plan Chontalpa, secando una gran extensión de terrenos inundables, debido principalmente a los represamientos del río Grijalva y del río Usumacinta. El agroecosistema marceño se adapta a las inundaciones, es altamente productivo, permite la resiliencia de los humedales, brinda importantes servicios ecosistémicos, como refugio de flora y fauna, así como una reserva de recursos alimentarios, hídricos y forestales que ejemplifican el manejo agroecológico del medio natural sin alterar los procesos naturales. En esta perspectiva, el manejo agroecológico maya chontal de los humedales de Tabasco, junto al sistema de milpa marceño, hay componentes naturales y culturales, tangibles e intangibles, cuya combinación moldea el carácter, e identifica al paisaje biocultural que forma parte de la identidad cultural de los tabasqueños. 2 ABSTRACT The milpero agroecosystems have adapted to a great diversity of ecosystems present in the Mexican territory, which represents the set of knowledge and biocultural knowledge generated by the various indigenous and mestizo groups of Mexico. This knowledge is reflected in traditional agricultural practices that have allowed the enormous diversity of native maize to be adapted and conserved in situ. The 65% of maize production in Mexico is grown under rainfed conditions. There is considerable risk due to the projected increases in temperatures, decreases in precipitation and increases in extreme meteorologic events related to climate change. The above will generate a significant impact on agricultural production, which represents one of the greatest threats to global food security. Traditional agroecosystems represent a strategic genetic and knowledge reservoir that will allow the generation of crop varieties and resilient food system strategies, adapted to the new environmental conditions that arise in the context of global climate change, in which the marceño agroecosystem is practiced in the alluvial plain of Tabasco. The first chapter describes the distribution of the marceño agroecosystem based on the terrain elevation. It was found that it is currently practiced in 203 rural Chontal and mestizo Mayan communities. By means of geographic information systems (GIS), bioclimatic variables and potential distribution models of 16 species of wild plants associated with the Marceño agroecosystem, the areas currently used for agricultural and livestock activities with cyclic floods were estimated, which have the potential to be converted to the marceño agroecosystem, as a productive strategy for adaptation to climate change. To estimate this information, a probability model of marceño occurrence was generated through MaxEnt, which was superimposed on a terrain elevation model (LiDAR) geoprocessed with GIS. The results obtained in this chapter show that the marceño agroecosystem is a current practice and is present in 203 locations in eight municipalities of Tabasco and it was estimated that this type of traditional agriculture is practiced in around 2% of the state area, at elevations of 1 at 7 meters. We estimate that the area with potential for reconversion to the Marceño system is around 18.4% of the state area. The implementation of this agroecosystem in a broader area is proposed, as an alternative for the development of agriculture and local food self-sufficiency and a strategy for the ecological restoration and ecosystem services of wetlands, as well as for the conservation of the biocultural landscape. from the lowlands of Tabasco. In the second chapter, the current cultural management tasks of the marceño agroecosystem were characterized, in the popal vegetation, which is practiced during the dry season of the year (from March to June) with the planting of the variety of native maize called mején. At the beginning of its cultivation in the swamps, the popal is cut and incorporated into the fertile and humid soils as fertilizer, which can improve its physical- chemical properties, allowing flooded plots (15-30 days of flooding) and swamp (6–8 months of flooding), be highly productive, since in the present work a planting density of 3 34,339 to 47,4004 plants ha–1 was estimated, which produced a yield of 3.3 Mg ha–1 of native maize mején grain, at a very low cost ($94.75 to $246.28 USD ha−1) and with a reduced use of inputs external to the system. The main attributes of seed selection and the predilection of the native variety of maize mején in the region are eight characteristics: the flavor of the dough, the yield of the cob, the height of the cob with respect to the ground, the ease of shelling, the grain flavor in food and the diameter of the cob. Likewise, a morphological characterization of the cobs and plants of the native maize mején was carried out. Based on morphological data from 36 cob accessions, we identified that the agroecosystem maintained an important diversity of native maize mején. One of the relevant morphological characteristics of the plant of this maize is the height of the cob on the plant (1.88 ± 0.20 m), which allows the farmer to bend the maize cane below the cob to start its drying without contact with the body of water during floods and thus the dry cobs can be harvested in floodimg presence. Finally, this work shows the floristic composition associated with the flooding areas, swamps and the Marceño agroecosystem, 144 species of hydrophytes and flood-tolerant plants are listed, which are associated with this agricultural system, which allows us to talk about the resilience of the current management of the agroecosystem and the cultural values related to this agricultural system, as well as conservation in situ of the native maize variety mején by farmers who maintain alive the traditional knowledge of the popal management in the swampy areas of Tabasco. This agroecosystem of pre-Hispanic origin allows the harvest to be carried out on foot, in canoes or on horseback during the rainy season, despite of the management of the swamps with this agroecosystem their use declined in the 90's, when the Chontalpa Plan, drying out a large area of floodplains, mainly due to the damming of the Grijalva and the Usumacinta Rivers. The marceño agroecosystem adapted to floods, is highly productive, allows the resilience of wetlands, provides important ecosystem services, as a refuge for flora and fauna, as well as a reserve of food, water and forest resources that exemplify the agroecological management of the environment without altering drastically natural processes. In this perspective, the Chontal Mayan agroecological management of the Tabasco wetlands, together with the marceño milpa system, there are natural and cultural components, tangible and intangible, whose combination shapes the character, and identifies the biocultural landscape that is part of the cultural identity of the Tabasco people. 4 INTRODUCCIÓN GENERAL Caracterización funcional y ecología del maíz mején en Comalcalco, Tabasco Grupos culturales, agroecosistemas y agrobiodiversidad en México Dentro del territorio mexicano, un importante número de pueblos originarios y expresiones culturales ha interactuado y manejado por miles de años la vasta diversidad biológica presente en los ecosistemas. En Mesoamérica se ha estimado el uso y manejo de entre 5,000 y 7,000 especies de plantas nativas (Casas et al., 1994), de las cuales se han domesticado más de 200, y manejado de manera incipiente al menos 700 (Casas et al., 2007; Blancas et al., 2010). México es considerado uno de los centros de origen de alrededor del 15% de las especies vegetales empleadas en el sistema alimentario mundial, entre las que destacan el maíz, el frijol, la calabaza, el jitomate y el chile, entre otras (CONABIO, 2007; Boege, 2008). El constante manejo de los ecosistemas por los diferentes grupos culturales para la producción de alimentos ha dado paso a sistemas agrícolas complejos denominados agroecosistemas, adaptados a diversos contextos ecológicos, cuyo origen y mantenimiento se encuentran estrechamente asociados a las actividades humanas, permitiendo la modificación de los territorios y creando paisajes bioculturales propios de cada región y grupo cultural (Denevan, 1995; Casas et al., 1999; Casas et al., 2007; Sans, 2007; Boege 2008; Moreno-Calles et al., 2013). La antigüedad de las actividades, el manejo humano de los ecosistemas y el ritmo pausado al que se han desarrollado las diversas etapas de la 5 agricultura, han permitido un notable acoplamiento entre las prácticas agrícolas y los nuevos ecosistemas creados por el hombre (novel ecosystems) (Sans, 2007; Hobbs et al., 2009). En Mesoamérica se desarrollaron habilidades técnicas culturales que permitieron la domesticación, diversificación y adaptación del maíz a las distintas condiciones ambientales (Doebley, 1990; Matsuoka et al., 2002; Piperno et al., 2009; Ranere et al., 2009), como resultado del profundo conocimiento que las civilizaciones prehispánicas poseían de su entorno natural. Centro de origen, domesticación y diversificación del maíz Como se mencionó anteriormente, México es centro de origen, domesticación y diversificación del maíz (Zea mays L.). Las evidencias moleculares han demostrado que el proceso de domesticación ocurrió entre 9,000 y 10,000 años atrás, a partir de una especie anual de teocintle (Zea mays ssp. parviglumis) nativa del valle del río Balsas, en la vertiente del Pacífico, en los estados de Michoacán y Guerrero, y desde ahí se dispersó y diversificó a lo largo y ancho del continente americano. La evidencia arqueológica más antigua que se tiene del maíz fue hallada en la cueva de Guilá Naquitz, Oaxaca, la cual tiene alrededor de 6,250 años de antigüedad, aproximadamente 700 años más que los especímenes de maíz más antiguos reportados para el Valle de Tehuacán (Benz, 2001;Sánchez et al., 2008; Kato et al., 2009; Piperno et al., 2009). Las diferentes evidencias encontradas hasta la actualidad, así como los estudios arqueológicos y antropológicos, señalan que antiguas civilizaciones mesoamericanas basaban su alimentación y cultura en torno al cultivo de maíz (Benz, 2001; Matsuoka et al., 2002; Sánchez et al., 2008; Kato et al., 2009; Piperno et al., 2009). Actualmente la mayor diversidad de maíz en el mundo se concentra en el territorio 6 mexicano, ya que se han reportado alrededor de 64 razas (CONABIO, 2011), de las cuales 59 son nativas (Sánchez et al., 2000). Sin embargo, no hay un acuerdo entre los especialistas en cuanto al número de razas de maíz, pues Ortega et al. (1991) reconoce solo 41, mientras que otros autores han propuesto razas de maíz nuevas (Aragón et al., 2006; Carrera et al., 2012). Esta importante diversidad de maíces nativos ha sido conservada in situ gracias a las distintas formas de hacer milpa o agroecosistemas tradicionales conformados por el policultivo, donde el maíz es el cultivo principal, intercalado con diversas especies de frijol, calabaza, chile y tomate, además de especies silvestres de quelites y quintoniles, que se han utilizado como alimento desde el periodo prehispánico y que en la actualidad forman parte de la dieta complementaria de las familias rurales de México (Boege, 2008; Linares y Bye, 2015; Dzib-Aguila et al., 2016). La resiliencia de los agroecosistemas ante el cambio climático global En México, el agroecosistema milpa se ha practicado aproximadamente desde hace ∼7,000 a 8,700 años (Mangelsdorf et al., 1967; Piperno et al., 2009), en una variedad de entornos y condiciones topográficas que involucra sistemas dependientes de riego y de temporal, que incluyen el manejo de pendientes pronunciadas con sistemas de terrazas o metapantles (Sánchez, 2012), así como una alta variedad de sistemas agroforestales asociados a parches de bosques, como la milpa-cactáceas-columnares y los tlacololes en las laderas cercanas a la cuenca del río Balsas (Casas et al., 1999; Moreno-Calles et al., 2013). Por otro lado, en los humedales del centro de México se practicó a gran escala la milpa en los agroecosistemas chinamperos y el calal (Wilken y Hernández-Xolocotzi, 1978; Rojas- Rabiela, 1993); en la costa del Golfo el tlapachol y el chamil los cuales emplean la 7 humedad residual de los suelos (Coe y Diehl, 1980); en la costa del Pacífico los tecallis (Armillas, 1984; Del Amo et al., 1988), y en las planicies aluvial de Tabasco, en las extensas áreas de humedales se practica la milpa de pantano conocida como el agroecosistema marceño (Orozco-Segovia y Gliessman, 1979; Peraza-Villarreal et al., 2019). La adaptación de los agroecosistemas milperos a una gran diversidad de ecosistemas es el resultado de los conocimientos y habilidades ancestrales de las y los agricultores indígenas y mestizos de México. La milpa representa una expresión biocultural de conocimientos, tecnologías y prácticas agrícolas que han permitido satisfacer las necesidades básicas de las familias campesinas, así como adaptar y conservar in situ una enorme diversidad de maíces nativos característicos de cada región y grupo cultural (Boege, 2008). Como se describió anteriormente, la relación pluricultural y de biodiversidad en los territorios de México, así como los aspectos culturales, sociales y económicos han permitido la generación y conservación de una importante diversidad genética del maíz, adaptada a una gran variedad de regiones agroclimáticas, permitiendo el cultivo en un amplio rango altitudinal que va desde los 0 m.s.n.m hasta los 3,200 m.s.n.m (Sanchez et al., 2000; Boege, 2008; Kato et al., 2009; Álvarez-Buylla y Nelson, 2013). En otras regiones del planeta se tienen reportes de cultivo de maíz incluso por debajo del nivel del mar, en las planicies del Caspio (−28 m.s.n.m., Naderi et al. 2013), hasta cerca de los 3,600- 3,900 m.s.n.m. en la meseta del Collao, alrededor del Lago Titicaca, en Perú y Bolivia (Salhuana, 2004; FAO, 2023). A raíz de la revolución verde, el modelo agroindustrial ha ido desplazando y relegando los conocimientos y saberes en torno a los agroecosistema tradicionales, estrechamente vinculados a los pueblos que han generado y conservado la agrobiodiversidad (Boege, 8 2008; Singh y Singh, 2017). En la actualidad se estima que, durante el último siglo, aproximadamente el 75% de las variedades de los cultivos nativos asociados a los agroecosistemas tradicionales se han perdido como una consecuencia del acelerado proceso de sustitución de las variedades nativas por variedades mejoradas empleadas en los sistemas agroindustriales (FAO, 2016; Casas, 2019). La pérdida de la agrobiodiversidad implica la pérdida de especies o de variedades adaptadas a un contexto ecológico y cultural particular, así como de los agroecosistemas en los que se reproducía cíclicamente la agrobiodiversidad (Casas, 2019). Este proceso de erosión genética preocupa particularmente en las regiones y comunidades agrícolas con mayor historia de manejo de cultivos que han sido reconocidas como centros de origen (Casas y Parra, 2007), como es el caso de México con el maíz. Por otro lado, el modelo de agricultura industrial ha llevado a la ruptura y disolución de las relaciones entre la agricultura tradicional, la cultura rural y la funcionalidad de los ecosistemas, y es la causa de la crisis ambiental y la transformación drástica de numerosos territorios rurales (Sans, 2007; Hobbs et al., 2013). Asimismo, las cadenas de distribución comercial y gubernamental de semillas mejoradas no han conseguido permear y ser adoptadas por los agricultores, pues estas no logran cumplir con sus preferencias culturales y agronómicas, ni adaptarse a las condiciones climáticas adversas propias de la agricultura de temporal (Bellon et al., 2014). Lo anterior se debe a que el maíz nativo se adapta a microambientes muy diversos en los que los maíces híbridos no representan una alternativa viable (Bellon et al., 2011; Bellon y Hellin, 2011). Por eso resulta preponderante el estudio y la caracterización de los agroecosistemas tradicionales de origen prehispánico, aún practicados en el territorio mexicano (Moguel y Toledo, 1999; Boege, 2008; Moreno-Calles et al., 2013; Casas et al., 2014). El 65% de la 9 producción de maíz en México (~7 a 8.5 millones de hectáreas) se cultivan bajo condiciones de temporal (Turrent, 2008), y de ellas se obtienen alrededor de 26.5 millones de toneladas de grano de maíz (SIAP-SADER, 2022). El consumo nacional ronda los 39 millones de toneladas, por lo que el déficit se soluciona con importaciones de grano de los Estados Unidos, en su mayoría de maíces genéticamente modificados, lo cual representa un riesgo a la salud humana y a la diversidad genética de los maíces nativos (Santiago y Mayorga, 2022). Por otra parte, el cultivo de maíz en México tiene un riesgo considerable debido al aumento previsto de las temperaturas y los fenómenos meteorológicos extremos, y la disminución de las precipitaciones, en relación con el cambio climático (Altieri et al., 2015; Ureta et al., 2020). El IPCC (2014) afirma que tanto la variabilidad del clima propio de cada región como el cambio climático (CCG) impactarán sobre la producción de alimentos a nivel global. Los modelos climáticos estiman que la temperatura global aumente 1.5°C entre 2030 y 2052 si el incremento continúa al ritmo actual (IPCC, 2019). El impacto que esto tendrá representa una de las mayores amenazas para la seguridad alimentaria mundial (Arnés et al., 2013; Nicholls et al., 2015; Challinor et al., 2016; Estrada et al., 2022). Bajo este escenario, la memoria biocultural y la agrobiodiversidad resguardada por los pueblos originarios y comunidades campesinas, representa un imprescindible y estratégico reservorio genético para la generación de nuevas variedades (Boege, 2008; Casas, 2019). En el caso del maíz nativo, será la estrategia fundamental para la generación de variedades mejoradas que permita hacer frente a las condiciones climáticas impredecibles del CCG (Altieri y Nicholls, 2011; Altieri et al., 2015; Ureta et al., 2020). Dentro de la gran diversidad de maíz nativo existe un importante reservorio genético sin explorar cuyo estudio puede encaminarse al mejoramiento genético convencional de nuevas variedades 10 más adaptables ante factores de estrés ambiental como la sequía, la salinidad del suelo y las inundaciones, esto con el objetivo de producir grano en ciclos cortos, para garantizar al mismo tiempo un alto valor nutricional y altos rendimientos, lo que será clave para responder ante los cambios ambientales y socioeconómicos, mitigar el riesgo climático y abastecer la demanda de alimentos a futuro (Dzib-Aguila et al., 2016; Eakin, 2000; Bellon et al., 2011; Bellon y Hellin, 2011;Ortega-Paczka, 2021). El maíz nativo mején y el agroecosistema marceño La variedad de maíz nativo conocido como mején es cultivado en los humedales de Tabasco por los mayas yoko yinikob (mayas chontales de Tabasco) y agricultores tradicionales. Es idóneo para terrenos pantanosos por su ciclo corto de 3 meses 15 días que le permite evadir las inundaciones y hacer uso de la humedad residual y fertilidad del suelo del pantano durante el periodo seco del año. La milpa se siembra en la medida que el nivel del agua de los humedales deja libre la superficie del pantano. A partir de ese momento el cultivo depende de la humedad residual del suelo. Esta variedad ha sido conservada in situ por los agricultores que han mantenido vivas las prácticas de manejo tradicional del agroecosistema marceño hasta la actualidad (Orozco-Segovia y Gliessman, 1979; Peraza-Villarreal et al., 2019). Sluyter (1994) menciona que el agroecosistema marceño podría haber sido un 'ciclo agrícola oportunista', dada su alta productividad que dependía del régimen natural de humedad residual del suelo de pantano. Si las inundaciones tempranas no se presentaban, sin embargo, la pérdida de la cosecha por inundación se podía compensar con las cosechas estacionales de las tierras de mayor elevación. En este sentido, para la conservación de la diversidad genética de los maíces nativos y 11 otros cultivos, es fundamental la continuidad de las prácticas culturales en torno a los agroecosistemas tradicionales, que reproducen y adaptan ciclo tras ciclo la agrobiodiversidad, con el manejo y selección campesina de las semillas (Brush, 1995; Mooney y Hunt, 2009; Altieri y Merrick, 1987). Los agroecosistemas tradicionales son importantes reservorios de la diversidad genética de los cultivos y de los conocimientos entorno al manejo de la agrobiodiversidad, así como de los territorios donde se experimentan continuamente diferentes estrategias de domesticación y manejo del paisaje (Boege, 2008; Achtak et al., 2010; Moreno-Calles et al., 2013; Casas et al., 2016). La acumulación de conocimientos y estrategias campesinas del manejo agroecológico, han requerido de la modificación de los ecosistemas y la posterior domesticación del paisaje, sin alterar drásticamente los procesos ecológicos de éstos. Lo antes mencionado, permite que los agroecosistemas tradicionales tengan una mayor capacidad de resiliencia ante fenómenos meteorológicos extremos en contraste con los sistemas agrícolas modernos de monocultivo y altamente tecnificados (Moguel y Toledo, 1999; Toledo y Barrera-Bassols, 2008; Arnés et al., 2013; Nicholls et al., 2015). Es decir, las prácticas agroecológicas empleadas dentro de los agroecosistemas tradicionales reducen su vulnerabilidad ante las inclemencias climáticas, debido a la diversificación de cultivos que mantienen la diversidad genética local. Agnoletti y Rotherham (2015) y Bezaury Creel et al. (2015) mencionan que para la conservación de la biodiversidad, la relación entre los pueblos originarios y las comunidades locales deben incluir el concepto de diseño de paisajes bioculturales sustentables. Lo que representa aquellos paisajes con una identidad característica propia del ecosistema y del grupo cultural que lo ha manejado durante siglos (Casas et al., 1996; Vallejo et al., 2014; Ichikawa, 2018; López et al., 2022). En México, a pesar de que la producción de maíz en pequeña escala en los sistemas tradicionales no representa una de las 12 principales fuentes de ingreso económico para las familias campesinas, sí cumple una importante función en términos de seguridad alimentaria (Martínez-Domínguez et al., 2017; Bellon et al., 2019). El agroecosistema marceño en Tabasco: pasado y presente En el manejo tradicional del agroecosistema marceño (cultivo de bajiales, de popalería, milpa de pantano o marceña) se cultiva el maíz nativo mején en los humedales de Tabasco, en el sureste de México, dadas las características climáticas de altas precipitaciones (2,900- 3,000 mm anuales) y de la poca elevación del terreno de la planicie aluvial tabasqueña (0-5 m s.n.m), así como de los numerosos cuerpos de agua que avenan esta región, que en época de lluvias se desbordan cíclicamente provocando aluviones que inundan los terrenos y forman pantanos temporales y mantienen los permanentes (Joaquín Bueno et al., 2005; Peraza-Villarreal et al., 2019). Este agroecosistema fue reportado inicialmente en la década de los 70's con los trabajos de Orozco-Segovia y Gliessman, 1979 y Orozco-Segovia y Vázquez-Yanes, 1980), en los cuales se proponía como una opción de manejo de los humedales altamente productivo en términos de rendimiento de maíz en grano para una región con continuas inundaciones y abundante vegetación de popales, así como con abundancia de especies hidrófilas de valor ecológico y cultural. En dichos trabajos se reportó la práctica de este agroecosistema en los humedales densamente cubiertos con una asociación de hidrófitas emergentes en la que la especie dominante es Thalia geniculata L., conocida localmente como popal, especie herbácea que mide de 1 a 3 m de altura, dependiendo del estado de conservación de la vegetación y de las características hidrológicas y edafológicas del terreno (Mirya y Hernández-Xolocotzi, 1963). 13 Posteriormente, Mariaca (1993) retomó el estudio del agroecosistema marceño, reportando las labores culturales y las comunidades en las que se practicaba el agroecosistema. En contraste con los trabajos mencionados anteriormente, en la actualidad las áreas cubiertas por popal han sido perturbadas o han disminuido su superficie, dadas las obras de drenado de una gran extensión de la planicie para el cultivo de pastos para la ganadería extensiva, así como a la constante quema de los popales y la urbanización de los humedales. A pesar de ello actualmente en las áreas cíclicamente inundables de Tabasco es posible encontrar viva la práctica del agroecosistema marceño (Peraza-Villarreal et al., 2019). Es posible que el agroecosistema marceño tenga un origen prehispánico, dada la presencia de fitolitos de maíz recuperado en San Andrés, Tabasco, con una antigüedad de ∼7.300 años, que demuestra la aparición temprana de la agricultura olmeca en las tierras bajas y pantanosas de Tabasco (Palerm y Wolf, 1958; Pohl et al., 2007). Por otro lado, las características propias de la agricultura indígena maya, en la que se hace uso del fuego para limpiar la parcela de un palo sembrador o macana. La distancia de siembra y número de semillas por golpe tienen también una fuerte raíz indígena (Morales y Perfecto, 2000). La alta densidad poblacional en la región durante el periodo prehispánico que sostuvo su alimentación a base de los abundantes recursos del entorno natural de los humedales, así como del cultivo de la milpa en los pantanos, previamente a la llegada de los europeos, refuerza la hipótesis de la práctica de la milpa en los pantanos. De acuerdo con West et al. (1985), se estima que durante el periodo prehispánico en el estado de Tabasco hubo una población de 135,000 a 300,000 habitantes, que probablemente cubrían su demanda de alimentos con una producción agrícola intensiva en los humedales de la llanura costera del Golfo sur de México. 14 La agricultura extensiva se practica hoy en día en los humedales mesoamericanos, y sin duda así fue durante el periodo prehispánico. Sin embargo, a pesar de que el agroecosistema marceño pudo ser una práctica agrícola extensiva en los vastos humedales tabasqueños, la modificación del entorno es de tipo efímera en comparación con los campos drenados y las chinampas de la costa del Golfo y del centro de México respectivamente, dada la poca infraestructura necesaria para su práctica, lo que genera pocas modificaciones y perturbación del paisaje (Sluyter, 1994). Durante el período prehispánico las poblaciones maya-chontal y nahuas se asentaron en la llanura aluvial de Tabasco, en la región de la Chontalpa y el territorio denominado Potonchán, en los actuales municipios de Cárdenas, Huimanguillo, Nacajuca, Cunduacán, Paraíso, Jalpa de Méndez y Comalcalco, en una extensión de terreno con elevaciones de 0 a 15 m.s.n.m., interconectados por una amplia red fluvial (West et al., 1985). Esto coincide con los registros de asentamientos prehispánicos dentro de los territorios dominados por los yoko yinikob, que se distribuyeron en zonas próximas a los ríos del sistema Grijalva- Mezcalapa (West et al., 1985). En estas localidades el agroecosistema marceño se practica en la actualidad, lo que refuerza que su práctica en las tierras bajas de Tabasco puede tener un origen prehispánico en el área maya Chontal. La práctica del agroecosistema marceño no modifica drásticamente el paisaje, pero a veces incluye el corte y quema de la vegetación herbácea acuática y la posible construcción efímera de sistemas de drenaje de control. No obstante, no hay una evidencia tangible en el paisaje, como las modificaciones del terreno en la Cuenca del Río Candelaria, Campeche (campos elevados, Thompson, 1974; Siemens, 1989). La presencia de grandes extensiones de terreno configuradas con vestigios de plataformas y canales de drenaje es una constante en la llanura costera del 15 Golfo de México, en las extensas áreas con inundaciones estacionales donde la agricultura de inundaciones recesivas en los humedales debió haber estado entre las principales adaptaciones agrícolas en la región. Diferentes autores, como Palerm y Wolf (1958), Puleston (1977, 1978), Turner (1974) y Denevan (1995), han discutido ampliamente la evidencia del desarrollo de la agricultura de regadío en 1os humedales, dada la configuración del paisaje de las tierras bajas del Golfo de México, que muestran vestigios con un patrón de modificación antropogénica del terreno, con una compleja red de campos elevados. El cultivo del maíz mején resulta idóneo para Tabasco, un estado que posee una gran extensión de humedales con el 27.76 % de su superficie ocupada por estos ecosistemas (Barba y Rangel-Mendoza, 2006). El desarrollo de conocimientos del entorno y las estrategias de manejo de los ecosistemas inundables, el régimen hidrológico en la zona, y sus cambios en el tiempo (p. e. CCG) resulta de gran interés para el manejo y reinserción de los agroecosistemas tradicionales, puesto que ejemplifican la experiencia en el manejo agroecológico del entorno natural, sin alterar drásticamente los procesos naturales, lo que permitiría conservar la resiliencia de los ecosistemas (Toledo y Barrera-Bassols, 2008; Altieri et al., 2015) en paralelo a la producción de cosechas con rendimientos altos y estables que permitan sostener las necesidades alimentarias de la población local. El agroecosistema marceño permite el eficiente aprovechamiento de los suelos fértiles de los pantanos, limita o anula la necesidad de insumos agrícolas externos al sistema. Orozco- Segovia y Vázquez-Yanes (1980) reportaron rendimientos de ∼4.5 Mg ha−1 de grano y ∼15 Mg ha−1 de rastrojo de maíz, lo que contrastaba con los rendimientos promedio de la cosecha de 1980 en Tabasco que fueron de ∼ 0.948 y 10 Mg ha−1 (con altos costos de 16 insumos agrícolas), respectivamente (SARH, 1980), hecho que demostraba que este agroecosistema era altamente productivo y resiliente preservando los humedales, las diferentes especies silvestres y la agrobiodiversidad (Peraza-Villarreal et al., 2019). Por otra parte, la variedad nativa mején presenta criterios o atributos fenológicos y morfológicos que la provee de cierta tolerancia-evasión de la inundación, como su ciclo de vida precoz y la altura de la mazorca en la planta, que permite que una vez doblada la planta de maíz, la cosecha de la mazorca pueda hacerse en cayucos o a caballo (Orozco-Segovia y Gliessman, 1979). Cambios sociales, ecológicos y políticos que incidieron en la dinámica hidrológica de la planicie aluvial de Tabasco y en la agricultura A las zonas inundables de Tabasco llegan principalmente los sedimentos de las cuencas de los ríos Usumacinta y Mezcalapa Grijalva que fertilizan amplias regiones, como ocurrió con el río Nilo en Egipto hace milenios. Tabasco registra una alta deforestación, sin embargo, ha sido considerada una región de baja erosión gracias a su orografía plana y a que sus principales ríos han sido represados (Servicio Geológico Mexicano, 2013). Al represamiento de los grandes ríos se le sumaron planes de desarrollo regional (Plan Chontalpa) que involucran el drenado de grandes superficies, el cambio del uso del suelo y el reparto agrario. Estas políticas culminaron principalmente en la década de los 60´s del siglo XX, aunque los planes para su construcción y el desarrollo regional se iniciaron décadas antes, a finales de los años 30 (Fuentes Aguilar, 1977). A este hecho se sumaron las políticas de modernización del campo que promovieron la sustitución de la tecnología tradicional por otras nuevas, en respuesta de las demandas del mercado nacional e 17 internacional, lo que repercutió en el cambio de la estructura productiva, fomentó la expansión de empresas comerciales y de organismos estatales que direccionaron la producción hacia sus propias metas y necesidades, aún a costa de los pequeños productores (Barkin 1977). Estas políticas y el drenado de grandes superficies hicieron que el aprovechamiento agrícola de los pantanos con el sistema del marceño y con ello el uso del maíz mején decayera, declarándose en vías de desuso en los 90's (Mariaca, 1996). Tabasco es uno de los estados más deforestados de México, ya que entre los años 1950 y 1990 perdió más del 90 % de su vegetación original a consecuencia del desarrollo de la agricultura industrial y la ganadería (Munguía, 2005). Estas actividades sustituyen la vegetación original por praderas cultivadas con pastos para la ganadería y para la agricultura de temporal, las cuales en la actualidad cubren más del 75 % de la superficie del estado (INEGI, 2013; Peraza-Villarreal et al., 2019). Gran parte de la vegetación acuática ha sido impactada por las actividades petroleras a causa de la canalización y el drenado del territorio que la reducen de manera severa (Novelo y Ramos, 2005); además muchos cuerpos acuíferos sufren procesos de eutrofización por las aguas residuales urbanas y acumulación de sedimentos (Hansen et al., 2007; De la Cruz et al., 2016). Cabe mencionar que el flujo natural del río Grijalva ha sido interrumpido por infraestructura hidráulica con fines agrícolas y por el desarrollo de vías de comunicación que cambian la dinámica del agua y los ciclos de inundación (Sánchez et al., 2015). Estas son algunas de las causas principales que alteran el equilibrio ecológico de los ecosistemas acuáticos en Tabasco (Novelo y Ramos, 2005; Sánchez y Barba, 2005). Sin embargo, a pesar de la existencia de presas como Chicoasén y Malpaso, en la actualidad aún se observan inundaciones cíclicas en la planicie aluvial de Tabasco (SEGOB-CENAPRED, 2009; Cotler et al., 2010) e inundaciones atípicas debido a la intensificación de fenómenos meteorológicos como El 18 Niño en 2007. o sequías severas que también causan graves daños económicos y sociales debido a la falta de infraestructura hidráulica en diversos municipios de Tabasco (SEGOB- CENAPRED, 2009). El excedente de agua de Villahermosa ha sido desviado hacia los municipios aledaños, lo que ha provocado que zonas que anteriormente eran utilizadas para la ganadería se inunden, igual que las riberas de los pantanos por lo que los agricultores han retomado el agroecosistema marceño a mayor escala en la región (Peraza-Villarreal et al., 2019). El marceño como una alternativa para la transición agroecológica Aumentar la producción agrícola para México es un tema de gran relevancia, pues el país busca lograr la autosuficiencia alimentaria, por lo que retomar, documentar y caracterizar el uso de variedades de maíz nativas de ciclo corto y con alto rendimientos como el mején, en el sistema productivo del marceño, representa una oportunidad para el desarrollo agrícola del sureste mexicano (Orozco-Segovia y Vázquez-Yanes, 1980). En este estudio, buscamos establecer el contexto histórico y el entorno actual del agroecosistema marceño en la llanura aluvial, así como documentar su práctica actual y potencial como una alternativa sostenible para la agricultura y la seguridad alimentaria. Se planteó el objetivo de medir la extensión de la práctica de este agroecosistema y estimar la superficie susceptible a inundaciones periódicas con potencial de reconversión productiva a este sistema, con la aspiración de establecer una estrategia de restauración ecológica y conservación del paisaje biocultural de Tabasco que permita el desarrollo sustentable de las comunidades rurales con potencial de inundaciones. En esta perspectiva, el manejo agroecológico maya chontal de los humedales de 19 Tabasco, junto al sistema de milpa marceño, tiene componentes naturales y culturales, tangibles e intangibles, cuya combinación moldea el carácter, identificándose como un paisaje biocultural (Boege, 2008; Baiamonte et al., 2015) que forma parte de la identidad cultural de los tabasqueños (Orozco-Segovia y Gliessman 1979; Peraza-Villarreal et al., 2019). Preguntas de investigación Capítulo I: The Marceño Agroecosystem: Traditional Maize production and Wetland Management in Tabasco, México. 1) ¿Cuáles son las localidades en las que actualmente se practica el manejo tradicional del agroecosistema marceño? 2) ¿Los sistemas de información geográfica, de imágenes Lidar de superficie de elevación del terreno del estado de Tabasco, permiten identificar las áreas con inundaciones cíclicas y la vegetación asociada al agroecosistema marceño? 3) ¿Es posible determinar la distribución potencial de la vegetación asociada al agroecosistema marceño con las imágenes Lidar y el software Maxent? 4) ¿Con base en la información obtenida se puede determinar la superficie potencial para la implementación del agroecosistema marceño en el estado de Tabasco? Capítulo II: Human livelihoods and wetlands conservation improved for the traditional. 1) ¿Actualmente cuál es la vegetación asociada al agroecosistema marceño? 2) ¿Cuáles son las características del suelo donde se practica el agroecosistema marceño? 20 3) ¿Cuáles son las características fisicoquímicas del agua que inunda las zonas donde se cultiva el marceño? 4) ¿Cuánta materia orgánica seca se incorpora al suelo de pantano antes y después del cultivo del maíz mején durante el ciclo marceño? 5) ¿Cuáles son las características morfológicas, los atributos de selección de las semillas del maíz mején y su preferencia entre la población? 6) ¿Cuál es el manejo agronómico tradicional actual del agroecosistema marceño? 7) ¿Cuál es el rendimiento del maíz mején en grano que se obtiene del agroecosistema marceño? 8) ¿Cuál es la diversidad morfológica de las mazorcas del maíz mején? 9) ¿Cuáles son los costos de producción del agroecosistema marceño con respecto a la agricultura mecanizada? 10) ¿La agricultura tradicional maya chontal representa una alternativa culturalmente adecuada que permita alcanzar la suficiencia alimentaria local en las tierras inundables de Tabasco? Hipótesis general Si el cultivo de la variedad de maíz nativa mején es altamente productivo en zonas pantanosas, entonces, al identificar las zonas del estado de Tabasco susceptibles de ser cultivadas con el agroecosistema marceño, podrá caracterizarse el agroecosistema en las condiciones ecológicas y socioeconómicas actuales y determinarse el arraigo por el cultivo del maíz mején y sus causas; su cultivo puede proponerse para obtener la autosuficiencia alimentaria en la región y en otras zonas inundables tropicales en general. 21 Objetivo general Entender la dinámica agroecológica en las zonas donde actualmente se practica el agroecosistema marceño en Tabasco, considerando el cambio hidrológico en la región, para calcular la superficie potencial cultivable y proponer estrategias para hacer su uso extensivo a otras regiones de México. Objetivos particulares 1. 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Citeseer. 37 CAPÍTULO I The Marceño Agroecosystem: Traditional Maize Production and Wetland Management in Tabasco, Mexico 38 sustainability Article The Marceño Agroecosystem: Traditional Maize Production and Wetland Management in Tabasco, Mexico Humberto Peraza-Villarreal 1,2, Alejandro Casas 3, Roberto Lindig-Cisneros 4 and Alma Orozco-Segovia 1,* 1 Laboratorio de Ecología Fisiológica, Instituto de Ecología, Universidad Nacional Autónoma de México, Mexico City, Coyoacán 04510, Mexico; hperazavillarreal@iecologia.unam.mx 2 Posgrado en Ciencias Biológicas, Universidad Nacional Autónoma de México, Mexico City, Coyoacán 04510, Mexico 3 Laboratorio de Manejo y Evolución de Recursos Genéticos, Instituto de Investigaciones en Ecosistemas y Sustentabilidad, Universidad Nacional Autónoma de México, Campus Morelia, Morelia, Michoacán 58190, Mexico; acasas@cieco.unam.mx 4 Laboratorio de Restauración Ambiental, Instituto de Investigaciones en Ecosistemas y Sustentabilidad, Universidad Nacional Autónoma de México, Campus Morelia, Morelia, Michoacán 58190, Mexico; rlindig@cieco.unam.mx * Correspondence: aorozco@ecologia.unam.mx; Tel.: +52-55-5622-9008 Received: 20 February 2019; Accepted: 1 April 2019; Published: 3 April 2019   Abstract: The marceño agroecosystem is based on traditional agriculture in the flooded areas of the alluvial plains of Tabasco, Mexico. In the marceño system, the native maize, called “mején”, is cultivated during the dry season using residual soil moisture. At physiological maturity, mején is tolerant to flooding. To estimate the potential area where marceño may be implemented, we characterized and defined the areas where it is practiced, using geographic information systems (GIS), and determined the bioclimatic variables of the sites where 16 species of wild plants associated with the management of the marceño grow. We also analysed areas of agriculture and livestock in relation to the cyclical floods. This information was used to generate a probability model of marceño occurrence through MaxEnt, which was superimposed on an elevation model (LiDAR) geoprocessed with GIS. The marceño was observed in 203 localities across eight municipalities of Tabasco (~2% of the state area), at elevations of 1–7 m. The calculated area with potential for implementation of the marceño is about 18.4% of the state area. The implementation of this agroecosystem on a wider area might be an alternative for local agriculture development and a strategy for ecological conservation and restoration of wetlands. Keywords: mején maize; Maya Chontal; Thalia geniculate; biocultural landscape; agroecosystem; wetland 1. Introduction Currently, there is a primary need worldwide to develop strategies for agriculture and the adaptation of smallholders to global climate change (GCC), in order to reach the goal of increasing food production by 50% by 2030, as proposed by the Food and Agriculture Organization (FAO) [1]. The adverse effects of GCC will be more severe in regions where millions of people depend on subsistence agriculture and are more vulnerable to food insecurity [2]. The increased frequency of severe weather events will have drastic consequences for agricultural production [2,3]. Lowlands can be highly productive in several countries around the world but require particular attention in order to understand their dynamics and risks, and the ways to prevent and respond to these risks. In Tabasco, Mexico, nearly 62% of people are highly marginalised and 45% have limited access to food, with their Sustainability 2019, 11, 1978; doi:10.3390/su11071978 www.mdpi.com/journal/sustainability 39 Sustainability 2019, 11, 1978 2 of 18 economy depending on subsistence farming [4,5]. Promoting productive practices that guarantee sufficient and diversified goods without irreversible deterioration of wetland ecosystems is therefore a priority [2]. Wetlands represent nearly 6% of the ecosystems worldwide [3,6]. Nevertheless, on a global scale, wetlands provide about 40% of global ecosystem services related to protection against floods, storm water retention, water quality enhancement, freshwater fisheries, food chain support, feeding grounds for juvenile marine fish, biodiversity maintenance, carbon storage and climate regulation [7,8]. However, these areas have been damaged by altering the hydrological and ecological watershed conditions of the basins due to agricultural and livestock expansion, as well as the effects of urbanisation on the hydrological system and contamination of water [7]. These activities require drainage of marshes or soil tillage, which result in negative environmental effects. This has increased interest in appropriate wetland management and its restoration [9,10]. Currently, recession agriculture is globally practiced in flooding areas in alluvial river plains, on lake margins and in other wetlands where water level changes are predictable. The overflow of the rivers promotes the seasonal deposition of sediments that increase fertility, which has been used in agriculture at the borders of several rivers such as the Nile, Euphrates, Tigris, Rhine, Danube, Po, Yangtze, Ganges, Mekong, Mississippi, Amazonas, and others. In flood recession agriculture, the water table falls during the dry season, which allows the residual moisture and natural fertility of the soil to be exploited, making high agricultural productivity possible. The crops are harvested before the rainy season, when the seasonal flood cycle of the wetlands starts [7,11]. Flood recession agriculture systems, such as recession sorghum in the Senegal Valley [12], the ponds of Dombes in France [13], and recession rice growing in Madagascar [14], are examples of the traditional use of wetlands for agriculture. In Mexico, the polyculture (maize–bean–squash) milpa system is managed in a variety of environments and topographic conditions involving irrigation or rain-fed agricultural systems [15]. In areas with periodic or permanent flooding dominated by wetland ecosystems, the milpa system is practiced in raising fields such as the chinampas and the calal systems in the Valley of Mexico [16,17], on the flooded banks of the Huazuntlán and Coatzacoalcos Rivers (both in the Coatzacoalcos Basin), where the systems are called tlapachol and chamil, respectively. They are both situated on the coastal plain of the Gulf of Mexico [18] and in the tecallis, on the banks of the Balsas River on the Pacific Coast of Mexico [19,20]. On the alluvial plains of Tabasco in the south-eastern Gulf of Mexico, the farming system marceño is a tropical milpa system, practiced as a traditional strategy of recessive flood agriculture [21]. The Maya Chontal farmers practice the marceño agricultural system as part of a general strategy of natural resource management, but in this study, we focus on the agroecosystem management and its actual and potential importance. This management system aims to modify and domesticate the landscape, without drastically altering the natural hydrological and ecological processes of flood-prone areas [22–24]. The Maya Chontal wetland management of the marceño agroecological system has tangible and intangible cultural and natural components, which shape the biocultural landscape of the Tabasco lowlands [25], as well as the food production and ecology of the lowlands in farming units. The alluvial plains of Tabasco are at an elevation of 0–5 m above sea level (a.s.l.), and are drained by numerous rivers, marshes, and lagoons. These plains are regularly flooded, forming temporary swamps and alluvial deposits. The marceño (cultivo de bajiales) agricultural system is appropriate for such an ecologically dynamic situation. In the Chontalpa region of Tabasco, maize and squash are therefore cultivated in the dry season (March–June) on these saturated wet soils [21,26,27]. Typically, the native maize variety, called mején, is cultivated because it is well adapted to germinate in moist soils during the dry season, and it matures in 2.5–3.5 months, evading drought and flooding [27,28]. The mején maize yields about 4.5 ton ha−1 of grain and about 15 ton ha−1 of stems used as fodder [21]. The natural vegetation is associated with emerging hydrophytic plants, dominated by Thalia geniculata L. (locally called popal, which is 1–3 m in height) (Figure 1). 40 Sustainability 2019, 11, 1978 3 of 18 Sustainability 2019, 11, x FOR PEER REVIEW 3 of 21 The natural vegetation is associated with emerging hydrophytic plants, dominated by Thalia geniculata L. (locally called popal, which is 1–3 m in height) (Figure 1). Figure 1. Crop cycle of the marceño agroecosystem: (a) Popal vegetation dominated by Thalia geniculata; (b) T. geniculata is cut at the beginning of the dry season; (c) seedlings of mején planted among the popal mulch; (d) mején maize plants; (e) corn at physiological maturity of grains (grains full and moist), at the beginning of the rainy season; (f) initial reestablishment of aquatic plants. To promote the conservation of highly native varieties of maize, beans, and squash in the marceño agroecosystem, and to promote the maintenance of wetlands and their ecosystem services, the aims of this research were: (1) To characterize the marceño system environment, (2) to identify the localities where the system is practiced, and (3) to estimate flood-prone areas where this agroecosystem may potentially be implemented. Figure 1. Crop cycle of the marceño agroecosystem: (a) Popal vegetation dominated by Thalia geniculata; (b) T. geniculata is cut at the beginning of the dry season; (c) seedlings of mején planted among the popal mulch; (d) mején maize plants; (e) corn at physiological maturity of grains (grains full and moist), at the beginning of the rainy season; (f) initial reestablishment of aquatic plants. To promote the conservation of highly native varieties of maize, beans, and squash in the marceño agroecosystem, and to prom te the maintenance of wetlands and th ir ecosystem services, the aims of this res arc wer : (1) To haracterize the marceño system environment, (2) to id ntify the localities where the system is practiced, and (3) to estimate flood-prone areas where this agroecosystem may potentially be implemented. 2. Materials and Methods 2.1. Study Sites This study covered eight municipalities of the alluvial plain of Tabasco, at elevations of −2 m to 15 m a.s.l. that are prone to cyclical flooding: Cárdenas, Huimanguillo, Comalcalco, Cunduacán, 41 Sustainability 2019, 11, 1978 4 of 18 Jalpa de Méndez, Nacajuca, Centla, and Jonuta (Figure 2). Tabasco is located in the basin of the Papaloapan, Grijalva-Mezcalapa, and Usumacinta Rivers, in the south of the Gulf of Mexico [26]. They form a complex net of deltaic channels interconnected with lakes, seasonal wetlands and marshes, which are interconnected from September to February. Moreover, 96% of the territory of Tabasco is on the coastal alluvial plains of the Gulf of Mexico [29]. The climate is warm–humid [30], with high precipitation during summer months, and an annual mean rainfall of 1500–2980 mm. Annual mean temperature during the dry season (March to June) is 25–30 ◦C. Before the middle of the 20th century, the area was about 50% covered by permanent and semi-permanent wetlands [26,28,29] and most of the remaining area was covered by tropical rainforests. Currently, only relics of these ecosystems exist because of anthropic disturbances, such as expansion of the agricultural and livestock frontier and the construction of dams [28,29]. Other relevant vegetation types are flooded rain forest, savanna and mangrove forest [29,31]. The soils in this area are vertisol, gleysol, cambisol, arcisol, luvisol, and fluvisol [32]. Sustainability 2019, 11, x FOR PEER REVIEW 4 of 21 2. Materials and Methods 2.1. Study Sites This study covered eight municipalities of the alluvial plain of Tabasco, at elevations of −2 m to 15 m a.s.l. that are prone to cyclical flooding: Cárdenas, Huimanguillo, Comalcalco, Cunduacán, Jalpa de Méndez, Nacajuca, Centla, and Jonuta (Figure 2). Tabasco is located in the basin of the Papaloapan, Grijalva-Mezcalapa, and Usumacinta Rivers, in the south of the Gulf of Mexico [26]. They form a complex net of deltaic channels interconnected with lakes, seasonal wetlands and marshes, which are interconnected from September to February. Moreover, 96% of the territory of Tabasco is on the coastal alluvial plains of the Gulf of Mexico [29]. The climate is warm–humid [30], ith high precipitation during su er onths, and an annual ean rainfall of 1500–2980 . nnual ean te perature during the dry season ( arch to June) is 25–30 ° . Before the iddle of the 20th century, the area as about 50 covered by permanent and semi-permanent wetlands [26,28,29] and most of the remaining area was covered by tropical rainforests. Currently, only relics of these ecosyste s exist because of anthropic disturbances, such as expansion of the agricultural and livestock frontier and the construction of da s [28,29]. ther relevant vegetation types are flooded rain forest, savanna and angrove forest [29,31]. The soils in this area are vertisol, gleysol, ca bisol, arcisol, luvisol, and fluvisol [32]. Figure 2. Location of the state of Tabasco: (a) Ombrogram of the study area, (b) the municipalities studied: 1. Huimanguillo, 2. Cárdenas, 3. Comalcalco, 4. Cunduacán, 5. Jalpa de Méndez, 6. Nacajuca, 7. Centla and 8. Jonuta; (c) the Mexico Valley and the Balsas and Coatzacoalcos Basins are also indicated. 2.2. Locating the Localities Where Marceño is Currently Practiced and the Potential Area for Its Implementation in Tabasco We reviewed the literature about the marceño system [21,27,28,33,34], as well as the data from the census of the Department of Agricultural Development of the municipality of Comalcalco and all areas reported that use the marceño agroecosystem in the flood-prone areas of Tabasco (Figure 2). To determine the localities that currently practice the marceño system, we undertook fieldtrips to identify the plots practising it and characterized the environment around the plots, including aquatic vegetation types, known locally as popales and tulares (vegetation dominated by Thalia geniculata L. Fig re 2. ti t st t f abasco: ( ) r r f t e st area, (b) the unicipalities studied: 1. i illo, 2. e as, 3. l lc , . , . , . 7. Centla and 8. Jonuta; (c) the M xico Valley nd the Balsas and Coatzacoalcos Basins are al o indicated. 2.2. Locating the Localities Where Marceño is Currently Practiced and the Potential Area for Its Implementation in Tabasco We rev ewed the literature about the marceño system [21,27,28,33,34], as well as the data from the census of the Department of Agricultural Development of the municipality of Comalcalco and all areas reported that use the marceño agroecosystem in the flood-prone areas of Tabasco (Figure 2). To determine the localities that currently practice the marceño system, we undertook fieldtrips to identify the plots practising it and characterized the environment around the plots, including aquatic vegetation types, known locally as popales and tulares (vegetation dominated by Thalia geniculata L. and Typha domingensis Pers, respectively) [21]. Additionally, we verified the practice of the marceño system in 80 plots within eight municipalities (Figure 2). These plots were georeferenced with a Global Positioning System (GPS, Garmin e-trex 30, Kansas, USA). The presence of the marceño system was confirmed by the smallholders of the plots, who were also asked about the characteristics of the agroecosystem, particularly the flooding regime of the system. 42 Sustainability 2019, 11, 1978 5 of 18 2.3. Modelling the Potential Distribution of Plant Species Associated with the Agroecosystem Using MaxEnt A model of the potential distribution of plant species associated with the marceño agroecosystem for the coastal plain of Tabasco was built as follows: (1) We included the plant communities associated with the agroecosystem located and georeferenced in the field and the historical occurrence of the 16 most frequent aquatic perennial herbs and tree species, both related to the agroecosystem and to the flood-prone areas of the alluvial plain of Tabasco [21] (Table 1); we also included the plant records for the Pacific and the Gulf coast of these species (a total of 3124 records, derived from the Global Biodiversity Information Facility website [35]). (2) We obtained 19 bio-environmental variables (Table 2) from the Bioclimas Neotropicales website [36] updated for Mexico, which compiles monthly climatic layers for the interval 1910–2009 (Table 2). We elaborated the model using the MaxEnt (Maximum Entropy Species Distributions Modelling, Version 3.33k [37]) algorithm that uses the function of minimum entropy to calculate distribution probabilities [38–40]. In this study, we only included the probabilities calculated for the state of Tabasco. Table 1. List of species, family and number of occurrences used for the distribution modelling of the marceño agroecosystem. Species Common Name Family Occurrences Cladium jamaicense Crantz Cerillo, sibal Cyperaceae 236 Cyperus articulatus L. Chintul Cyperaceae 377 Echinochloa crus-pavonis (Kunth) Schult. Camalote de agua Poaceae 65 Eleocharis cellulosa Torr. Junquillo Cyperaceae 47 Erythrina fusca Lour. Colorin Fabaceae 10 Haematoxylum campechianum L. Tinto Fabaceae 485 Hibiscus striatus Malva Malvaceae 10 Jacquinia aurantiaca W.T. Aiton Jaboncillo Primulaceae 207 Pachira aquatica Aubl. Zapote de agua Malvaceae 431 Panicum hirsutum Sw. Pelillo Poaceae 35 Phragmites australis (Cav.) Trin. Carrizo Poaceae 10 Sagittaria lancifolia L. Cola de pato Alismataceae 231 Salix humboldtiana Willd. Sauce Salicaceae 209 Scleria macrophylla J. Presl & C. Presl Navajuela Cyperaceae 30 Thalia geniculata L. Popal, hojilla Marantaceae 406 Typha domingensis Pers. Tule, nea Typhaceae 335 Total 3124 Table 2. Climatic variables used in the modelling of the potential distribution of thirteen wild species related to the marceño agroecosystem based on Bioclimas Neotropicales [36]. Bioclimate Variable Units Bioclimate Variable Units B1 = Annual mean temperature ◦C B10 = Mean temperature of warmest quarter ◦C B2 = Mean diurnal range (mean of monthly (max temp—min temp)) ◦C B11 = Mean temperature of coldest quarter ◦C B3 = Isothermality (B2/B7) × 100 ◦C B12 = Annual precipitation mm B4 = Temperature seasonality (standard deviation ×100) ◦C B13 = Precipitation of wettest month mm B5 = Max temperature of warmest month ◦C B14 = Precipitation of driest month mm B6 = Min temperature of coldest month ◦C B15 = Precipitation seasonality (coefficient of variation) mm B7 = Temperature annual range (B5-B6) ◦C B16 = Precipitation of wettest quarter mm B8 = Mean temperature of wettest quarter ◦C B17 = Precipitation of driest quarter mm B9 = Mean temperature of driest quarter ◦C B18 = Precipitation of warmest quarter mm B19 = Precipitation of coldest quarter mm 2.4. Generating the Terrain Elevation Model To generate the digital model of terrain elevation (−2.96 to 1146.25 m) for the state of Tabasco, we processed LiDAR images with ArcMap 10.2.1 Arc Gis Esri (1360 images in GRID format, E-15 region [41]). The horizontal resolution was 5 m. These models did not include infrastructure and vegetation in order to identify the localities that used the marceño agroecosystem. We used this model 43 Sustainability 2019, 11, 1978 6 of 18 of terrain elevation to locate low elevation areas (0–7 m) in order to determine the areas subject to flooding and with potential to implement the marceño system. 2.5. Modelling the Potential Areas for the Marceño Agroecosystem For this estimation, we included areas with both agriculture and pastures that naturally have floods and are therefore susceptible to productive reconversion to marceño. We used the SIG ArcMap software to geoprocess the following information: (1) To determine the flood-prone areas with elevations from 0 to 7 m, we used LiDAR images of terrain elevation [41]; (2) to identify flood-prone areas with agricultural and cultivated grass pastures, and to discard preserved areas with aquatic vegetation (marshes, mangroves, flooded rain forest, and permanently flooded areas), rain forest areas, natural protected areas, urban areas, infrastructure, and drained areas with elevations of 18–1146 m, we used the layers of soil—gleysol and vertisol (silty-clay with poor drainage and high organic matter content)—and vegetation [32,42]; (3) we used the layer of highest probabilities of distribution of plant communities associated with the marceño system (as generated in Section 2.3); (4) we also added a layer with the location of the Maya Chontal population, with the data collected from [43]; (5) we superimposed all five layers to determine the areas with potential to use the marceño agroecosystem including the pasture areas with potential for reconversion to agriculture, the ethnic origin of the population and their influence area (biocultural region [25]). 3. Results Location of the Marceño Agroecosystem in the State of Tabasco We located the presence of the marceño system in the field in 203 localities in the eight municipalities of Tabasco, particularly in Comalcalco, Nacajuca and Cunduacán (Table 3). According to the elevation model of the terrain (LiDAR), these localities are at elevations of 1−7 m with high precipitation (≥2980 mm). This high precipitation causes cyclic floods that maintain the seasonal swamps and other areas used for extensive cattle raising (Figure 3, Table 3, Table 4, and Table A1). Sustainability 2019, 11, x FOR PEER REVIEW 7 of 21 Figure 3. Map of the elevation of the terrain (−2 to 1146.25 m, see Table 4) and locations of the Tabasco localities, where the practice of the marceño agroecosystem occurs nowadays (■), aquatic vegetation patches of popal (■) and tular (■), drain channels (−) with Plan Chontalpa (−) and Plan Balancan- Tenosique (−), Villahermosa city (■). Table 3. Municipalities, number of localities (L), and elevation range (TER) where the marceño was located in Tabasco, Mexico. Total population (TP), indigenous population (IP), and percentage of indigenous population for each municipality (IP%). Municipality L TER (m a.s.l.) TP IP IP% Cárdenas 25 0−14 22,486 170 0.8 Centla 22 1−11 22,965 5851 25.5 Comalcalco 43 2−11 72,899 390 0.5 Cunduacán 31 3−10 29,823 154 0.5 Huimanguillo 12 6−10 9,670 32 0.3 Jalpa de Méndez 23 3−10 34,823 1133 3.3 Jonuta 12 0−11 10,337 640 6.2 Nacajuca 35 2−14 43,631 20,938 48 Total: 203 264,381 47,119 18 Table 4. Elevation range of the terrain in the state of Tabasco, Mexico. Elevation Range (m a.s.l.) Areas (km2) % Areas of the State of Tabasco <–2−0 3280.97 13.40 0−1 4455.37 18.19 1−5 5275.40 21.54 5−15 5351.14 21.85 15−20 1376.87 5.62 20−25 869.55 3.55 25−30 700.38 2.86 30−50 3234.04 13.21 50−100 1605.80 6.56 100−500 882.77 3.61 500−1,146 62.52 0.26 Up to 61.6% (15081.9 km2) of Tabasco is between 0 and 15 m a.s.l. Within this area, 16.6% is drained (2500 km2) and 13.4% (3280.97 km2) is permanently flooded (−2.96 to 0 m a.s.l.). We observed that the remaining aquatic vegetation covered 24% of the state (5902.48 km2). However, most of this Figure 3. Map of the elevation of the terrain (−2 to 1146.25 m, see Table 4) and locations of the Tabasco localities, where the practice of the marceño agroecosystem occurs nowadays (), aquatic vegetation patches of popal () and tular (), drain channels (−) with Plan Chontalpa (−) and Plan Balancan-Tenosique (−), Villahermosa city (). 44 Sustainability 2019, 11, 1978 7 of 18 Table 3. Municipalities, number of localities (L), and elevation range (TER) where the marceño was located in Tabasco, Mexico. Total population (TP), indigenous population (IP), and percentage of indigenous population for each municipality (IP%). Municipality L TER (m a.s.l.) TP IP IP% Cárdenas 25 0−14 22,486 170 0.8 Centla 22 1−11 22,965 5851 25.5 Comalcalco 43 2−11 72,899 390 0.5 Cunduacán 31 3−10 29,823 154 0.5 Huimanguillo 12 6−10 9670 32 0.3 Jalpa de Méndez 23 3−10 34,823 1133 3.3 Jonuta 12 0−11 10,337 640 6.2 Nacajuca 35 2−14 43,631 20,938 48 Total: 203 264,381 47,119 18 Table 4. Elevation range of the terrain in the state of Tabasco, Mexico. Elevation Range (m a.s.l.) Areas (km2) % Areas of the State of Tabasco <–2−0 3280.97 13.40 0−1 4455.37 18.19 1−5 5275.40 21.54 5−15 5351.14 21.85 15−20 1376.87 5.62 20−25 869.55 3.55 25−30 700.38 2.86 30−50 3234.04 13.21 50−100 1605.80 6.56 100−500 882.77 3.61 500−1,146 62.52 0.26 Up to 61.6% (15081.9 km2) of Tabasco is between 0 and 15 m a.s.l. Within this area, 16.6% is drained (2500 km2) and 13.4% (3280.97 km2) is permanently flooded (−2.96 to 0 m a.s.l.). We observed that the remaining aquatic vegetation covered 24% of the state (5902.48 km2). However, most of this area is currently disturbed. We calculated that in Tabasco, 2365.13 km2 are dominated by T. geniculata (popal) and 3537.36 km2 by T. domingensis (cattail, tular) (Figure 3). Data for each of the studied municipalities are presented in Table 5. Figure 4 shows the areas with high probability (0.807) for the distribution of plant communities associated with the marceño agroecosystem. This model, in conjunction with the terrain elevation model, provided us with information about the areas with potential for productive marceño agroecosystems. The area where the marceño agroecosystem is currently practiced had the greatest calculated potential (Figure 3, Figure 4b, and Table A1). 45 Sustainability 2019, 11, 1978 8 of 18 Table 5. Livestock and agricultural areas susceptible to cyclical flooding that have potential (very high, high and medium) to be converted into the marceño agroecosystem. Areas are shown with flooding potential and percentage, representing each municipality’s area. Cyclic Flooding Potential Area for Reconversion to Marceño Area with Wetland Vegetation Conserved (1) Elevation Terrain Range m a.s.l. 0−2 2−4 4−6 Municipality Very High High Medium Cultivated Grass Popal Tular km2 % km2 % km2 % km2 % km2 % km2 % Comalcalco 158.57 20.7 154.66 20.2 129.93 17 310.86 40.6 49.16 6.4 93.11 12.2 Cárdenas 323.23 15.8 83.59 4.1 133.85 6.5 550.01 26.9 66.27 3.2 161.72 7.9 Cunduacán 0.08 0.01 4.60 0.77 40.63 6.8 85.93 14.4 5.91 1.0 41.97 7.0 Nacajuca 105.78 19.8 62.93 11.8 51.72 9.7 242.80 45.5 106.93 20.0 126.38 23.7 Jalpa de Mendéz 63.39 17.2 67.55 18.3 89.69 24.3 119.19 32.3 43.46 11.8 36.21 9.8 Jonuta 135.35 8.2 211.33 12.9 166.81 10.2 513.49 31.3 226.97 13.8 343.33 20.9 Centla 232.26 8.6 6.12 0.23 0.15 0.01 237.40 8.8 163.00 6.1 1394.78 51.9 Centro 215.32 13.6 150.78 8.8 156.48 9.3 1044.78 61 33.99 2.0 303.33 17.7 Huimanguillo 280.72 7.6 157.96 4.3 145.69 3.9 583.22 15.7 147.02 4.0 151.62 4.1 Macuspana 194.26 8.0 190.13 8.0 90.12 3.7 1522.72 62.8 34.18 1.4 550.73 22.7 Paraíso 63.00 3.0 12.99 0.64 2.30 0.11 53.01 13.0 − − 30.67 7.5 Notes: (1) The areas originally covered by popal, were disturbed by clearance for agriculture, fires for turtle hunting, and cattle raising. Vegetation was substituted by aggressively introduced forages and weeds that cover vast areas with cyclic flooding. Additionally, the drainage of wetlands has dropped the phreatic level. 46 Sustainability 2019, 11, 1978 9 of 18 Sustainability 2019, 11, x FOR PEER REVIEW 10 of 21 Figure 4. Potential distribution of 16 aquatic plant species reported to be associated with the marceño agroecosystem. The model was built for both the Pacific and Gulf Mexico Costal regions to give robustness to the model (Table 1). The colours represent the potential probability of (a) the potential distribution model for all the areas included in the MaxEnt analysis; (b) the potential distribution model of distribution of the aquatic plant communities found in Tabasco where currently the marceño agroecosystem is practiced (●). Current Maya Chontal populations (▲). The geospatial analysis showed that approximately 1693.71 km2 has a very high potential for marceño (0–2 m a.s.l.). Considering the predictable periodicity of seasonal flooding, only about 1259 km2 has a high potential (2–4 m a.s.l.) because of its dependence on the severity of inundation. Moreover, approximately 1140.1 km2 has a moderate potential and 471.3 km2 has a low potential (4– 6 and 6–7 m a.s.l., respectively) because this area is susceptible to flooding in years with atypically high rainfalls. The estimated potential of the marceño agroecosystem formed approximately 18.4% of Tabasco’s area (Figure 5, Table 6). Figure 5. Agricultural and livestock areas in the Tabasco state with potential to be cultivated with the marceño agroecosystem. Probabilities of cyclic annual flooding occurrence (areas and elevations in the range −2 to 7 m) are indicated (see Table 6). i r . i t i ti l t i t i t it t ce t . e el s ilt f t t ifi lf i t l i t i r t t t l ( able 1). c l re rese t t t ti l r ilit f ( ) t e te ti l istri ti l f r ll t areas incl i the axE t analysis; ( ) the potential distrib ti el f istri ti f t e a atic la t c ities f i a asc ere c rre tl t e arce o agroecosyste is ractice (•). urrent aya Chontal populations (N). The geospatial analysis showed that approximately 1693.71 km2 has a very high potential for marceño (0–2 m a.s.l.). Considering the predictable periodicity of seasonal flooding, only about 1259 km2 has a high potential (2–4 m a.s.l.) because of its dependence on the severity of inundation. Moreover, approximately 1140.1 km2 has a moderate potential and 471.3 km2 has a low potential (4–6 and 6–7 m a.s.l., respectively) because this area is susceptible to flooding in years with atypically high rainfalls. The estimated potential of the marceño agroecosystem formed approximately 18.4% of Tabasco’s area (Figure 5, Table 6). Sustainability 2019, 11, x FOR PEER REVIEW 10 of 21 Figure 4. Potential distribution of 16 aquatic plant species reported to be associated with the marceño agroecosystem. The model was built for both the Pacific and Gulf Mexico Costal regions to give robustness to the model (Table 1). The colours represent the potential probability of (a) the potential distribution model for all the areas included in the MaxEnt analysis; (b) the potential distribution model of distribution of the aquatic pla communities found in Tabasco where currently the marceño agroecosystem is practiced (●). Current Maya Chontal populations (▲). The geospatial analysis showed that approximately 1693.71 km2 has a very high potential for marceño (0–2 m a.s.l.). Considering the predictable perio icity of seasonal flooding, only about 1259 km2 has a high potential (2–4 m a.s.l.) because of its dependence on the severity of inundation. Moreover, approximately 1140.1 km2 has a moderate potential and 471.3 km2 has a low potential (4– 6 and 6–7 m a.s.l., respectively) because this area is susceptible to flooding in years with atypically high rainfalls. The estimated potential of the marceño agroecosystem formed approximately 18.4% of Tabasco’s area (Figure 5, a le 6). Figure 5. Agricultural and livestock areas in the Tabasco state with potential to be cultivated with the marceño agroecosystem. Probabilities of cyclic annual flooding occurrence (areas and elevations in the range −2 to 7 m) are indicated (see Table 6). Figure 5. Agricultural and livestock areas in the Tabasco state with potential to be cultivated with the marceño agroecosystem. Probabilities of cyclic annual flooding occurrence (areas and elevations in the range −2 to 7 m) are indicated (see T ble 6). 47 Sustainability 2019, 11, 1978 10 of 18 Table 6. Potential area for the marceño agroecosystem in the lowlands of Tabasco, Mexico. Potential Elevation Range (m a.s.l.) Potential Area (km2) Total (km2) % Area of the State of Tabasco Very high 0–1 911.9 1693.7 6.851–1.5 420.7 1.5–2 361.1 High 2–2.5 330.3 1259.0 5.09 2.5–3 316.2 3–3.5 307.3 3.5–4 305.2 Medium 4–5 574.8 140.1 4.61 5–6 565.4 Low 6–7 471.3 471.3 1.91 Total: 4564.2 18.46 4. Discussion During the fieldwork, we corroborated the presence of the marceño agroecosystem in Tabasco’s rural communities, many of which have been inhabited by the Maya Chontal since pre-Hispanic times (Figures 3–5; Table 3). These localities are in the range of 1–14 m above sea level and are susceptible to seasonal flooding. Based on the reports of the Food Information Services of Tabasco [44], regarding the area of planted maize during the spring–summer cycle, it can be inferred from our model that, currently, the marceño system cover less than 463.52 km2, which represents approximately 10% of the potential area (Figure 5, Table 3). The presence of marceño had been reported in 183 localities previously [33], whereas we found it in 203 localities. However, there might be many other locations in rural areas that use the marceño agroecosystem, as it is a current practice in rural areas used by both Maya Chontal and Mestizo people. It is also possible that a greater number of localities practice the marceño system in the lowlands and nearby towns of Tabasco, on the banks of the Usumacinta River in the state of Campeche (locality of Palizada), given the cultural similarities of the region. The model of potential distribution of the plant communities associated with marceño allowed an estimation of the areas where the ecosystem is conducive to the implementation of the marceño agroecosystem as a rural development strategy in Tabasco. Marceño is cultivated predominantly to feed the Maya Chontal population. A total of 59% of this area is currently occupied by primary activities such as subsistence agriculture, mainly in the municipality of Nacajuca [43]. The management of the popal by the marceño agroecosystem is fundamental to the subsistence of this population. In Tabasco, there are 79694 Maya Chontal people (3.6% of the population) [43], 62% of which live within the “La Chontalpa” biocultural region [25]. This indigenous territory covers about 794.06 km2 (3.2% of the area of the state), mainly in the municipalities of Nacajuca and Centla. In this study, we found that important areas of wetland vegetation were considered as popal. Our results showed that, in this area, 269.93 km2 (11.4%) and 1521.2 km2 (43%) are covered with popal and tular, respectively (Figure 3, Table 4). It is relevant that approximately 7% of the Mayan Chontal territory is located within the Natural Protected Area of the “Reserva de la Biosfera Pantanos de Centla” (3027.06 km2) [45], one of the priority regions for the conservation of biodiversity and agrobiodiversity. This area has been protected by the Government of Mexico and the Ramsar Convention [46]. For that reason, we only used the areas actually used for cattle, and the marceño agroecosystem (using landraces, mainly mején), to calculate the potential areas for marceño. This conservation area protects against the construction of infrastructure for forced drainage that completely modifies the hydrology and the ecological cycles of wetlands [9,10]. In the marceño agroecosystem and other examples of extensive agricultural carried out in the wetlands, the combination of food production and ecosystem services in this area might contribute to the high resilience of both the wetlands and marceño system [21,24,27,28], which maintains other ecosystem services such as improving water quality, stopping floods, and maintaining biodiversity [7] and agrobiodiversity [9]. 48 Sustainability 2019, 11, 1978 11 of 18 Currently, there are examples of reactivation of pre-Hispanic agricultural systems in wetlands, such as the waru waru or suka kollus system in Lake Titicaca [47] and the implementation of the “chinampas chontales” in Nacajuca, Tabasco, which are similar to the chinampas system in the Valley of Mexico [48]. Similarly, the calculated potential areas for the marceño agroecosystem represent a viable alternative to produce food for ecological restoration programs of the lowlands of Tabasco and other tropical regions where the traditional cultivation of corn is the basis of the smallholders’ diet. Additionally, the marceño agroecosystem is recognized by the smallholders for its high soil fertility and good yield of corn crops in flooded areas (actually ∼4.3 ton ha−1 of grain, including native maize varieties such as mején). The characteristic abundance of popal in the hydrophilic vegetation of the landscape and culture of the Tabasco lowlands has been altered by a lack of interest and understanding of its cultural and ecological relevance, as well as a lack of knowledge about its management and productive potential. The marceño agroecosystem is part of the local biocultural identity and its maintenance and enhancement may also contribute to the conservation of the Tabasco wetlands and biocultural heritage. Abandoning the marceño agroecosystem would represent the loss of a unique agrobiodiversity and a biocultural landscape that represents the important identity of the Tabasco lowlands. On the other hand, the marceño might contribute to the tropical subsistence agriculture. This is relevant because the FAO reports that, in Central America, household traditional agriculture farmers produce about 50% of the agricultural production of the region and more than 70% of the foods. The findings of this study have an important implication for other wetland areas in Mexico and elsewhere in the world, such as the Rhine [49], Danube, and Mississippi [50] River basins. It could also be adopted as a model in agricultural development plans in other tropical regions with cyclical floods and food poverty. This would also allow in situ conservation of agrobiodiversity of varieties of crops that have adapted to high humidity conditions, such as maize mején, which represents a genetic reservoir for research on new varieties that are tolerant to waterlogging. Marceño represents an opportunity for agroecological studies that allows communities settled in areas susceptible to cyclical floods (61.6% of the state of Tabasco) to develop. This might allow sustainable development, which could be accompanied by ecological restoration programs and the conservation of the biocultural landscape of the Tabasco wetlands. 5. Conclusions Marceño is relevant for smallholders who produce food for self-consumption in one of the poorest and most vulnerable regions of Mexico. The adoption of practices of sustainable management of natural resources and the retention of traditional agricultural systems by smallholders has been proposed by the FAO as part of a strategy to adapt to climate change, eradicate global poverty and end hunger. The Intergovernmental Panel on Climate Change estimates that agronomic adaptation could improve yields by 15 to 18% [49]. This demonstrates the significance of household agriculture, such as marceño, for the food sovereignty of the smallholder communities [50,51]. In Tabasco, the maize crop occurs in the rainy season, but the marceño system occurs in the dry season, allowing an additional staggered agricultural cycle during the recession of the flood. This study improves the understanding of the current context of the marceño agroecosystem in the lowlands of Tabasco. Author Contributions: H.P.-V., A.O.-S., A.C. and R.L.-C. identified the research questions, analysed the data, and wrote the paper. Funding: This work was supported by the Universidad Nacional Autónoma de México (project DGAPA-PAPIIT IN-205715), the Consejo Nacional de Ciencia y Tecnología (project SEP-CONACyT-221015, the Doctor’s scholarship 334495 to Humberto Peraza Villarreal) and the Programa de Posgrado en Ciencias Biológicas, UNAM. Acknowledgments: We dedicate this research to the relevant agroecologists, Arturo Gómez-Pompa and Stephen Gliessman. We thank María de Jesús Ordoñez, María Esther Sánchez Coronado, José Gerardo Rodríguez Tapia, Alejandro René González Ponce, José Miguel Baltazar Gálvez, Luz Palestina Llamas Guzmán and Luis Vidal Pedrero López for technical support. 49 Sustainability 2019, 11, 1978 12 of 18 Conflicts of Interest: The authors declare no conflict of interest. Appendix A Table A1. Localities indicated in the Figure 3. Municipality Id Number and Locality Showed in Figure 3 Cárdenas 1.Arroyo Hondo 1ra. Sección (Santa Teresa A) 2.Arroyo Hondo Abejonal 3.Azucena 2da. Sección 4.Azucena 3ra. Sección (El Triunfo) 5.Azucena 4ta. Sección (Torno Alegre) 6.Buenavista 1ra. Sección 7.Buenavista 2da. Sección 8.Cárdenas 9.El Capricho 10.El Golpe 11.El Golpe 2da. Sección (Los Patos) 12.El Porvenir 13.Ignacio Gutiérrez Gómez (San Felipe) 14.Islas Encantadas (El Zapote y Reyes Heroles) 15.La Trinidad 16.Las Coloradas 2da. Sección (Ampliación las Aldeas) 17.Naranjeño 2da. Sección A 18.Nueva Esperanza 19.Paylebot 20.Poblado C-28 Coronel Gregorio Méndez Magaña Uno 21.Poza Redonda 1ra. Sección 22.Poza Redonda 4ta. Sección (Rincón Brujo) 23.Río Seco 1ra. Sección 24.Santana 2da. Sección A 25.Zapotal 1ra. Sección Centla 26. Buena Vista 27.Chichicastle 2da. Sección 28. Chichicastle 3ra. Sección 29.Cuauhtémoc 30.El Carmen 2da. Sección 31.El Guatope 32.El Limón (De Vicente Guerrero) 33.El Naranjal 34.El Porvenir 35.Gregorio Méndez Magaña 36.Hablan los Hechos (Santa Rosa) 37.Leandro Rovirosa Wade 1ra. Sección 38.Leandro Rovirosa Wade 2da. Sección 39.Nueva Esperanza de Quintín Aráuz 40.Potrerillo 41.Quintín Aráuz 42.Ribera Alta 1ra. Sección 43.Ribera Alta 3ra. Sección 44.San José de Simón Sarlat (El Coco) 45.Simón Sarlat 46.Tres Brazos 47.Vicente Guerrero 50 Sustainability 2019, 11, 1978 13 of 18 Table A1. Cont. Municipality Id Number and Locality Showed in Figure 3 Comalcalco 48.Arena 1ra. Sección 49.Arena 3ra. Sección 50.Arena 4ta. Sección 51.Arroyo Hondo 3ra. Sección 52.Belisario Domínguez 53.Carlos Greene 54.Carlos Greene 1ra. Sección Tres (Colonia el Limón) 55.Carlos Greene 4ta. Sección 56.Chichicapa 57.Cupilco 58.Cuxcuxapa 59.Francisco I. Madero 1ra. Sección 60. Francisco I. Madero 2da. Sección 61.Francisco Trujillo Gurría 62.Gregorio Méndez 1ra. Sección 63.Gregorio Méndez 2da. Sección 64.Gregorio Méndez 3ra. Sección 65.Guatemalán 66.Guayo 2da. Sección 67.Independencia 1ra. Sección 68.Independencia 2da. Sección 69.Independencia 3ra. Sección 70.José María Pino Suárez 1ra. Sección 71.Lagartera 73.León Zárate 1ra. Sección 74. León Zárate 2da. Sección 75.Norte 1ra. Sección (San Julián) 76.Novillero 4ta. Sección 77.Occidente 1ra. Sección 78.Occidente 2da. Sección 79.Occidente 3ra. Sección 80.Oriente 3ra. Sección 81.Oriente 6ta. Sección (Los Mulatos) 82.Paso de Cupilco 83.San Fernando (Pueblo Nuevo) 84.Sargento López 1ra. Sección 85.Sargento López 2da. Sección (El Chuzo) 86.Sargento López 3ra. Sección (San Jorge) 87.Sargento López 4ta. Sección 88.Tecolutilla 89.Tránsito Tular 90.Zapotal 2da. Sección Cunduacán 91.Alianza para la Producción 92.Anta y Cúlico (Santa Rita) 93.Buenaventura 94.Buenos Aires 95.Ceiba 1ra. Sección (Jahuactal) 96.Cúlico 1ra. Sección 97.Cumuapa 1ra. Sección 98.Dos Ceibas 99.El Palmar 100.El Tunal 101.Felipe Galván 102.General Francisco J. Mújica 103.Gregorio Méndez 104.Huimango 1ra. Sección 51 Sustainability 2019, 11, 1978 14 of 18 Table A1. Cont. Municipality Id Number and Locality Showed in Figure 3 Cunduacán 105.La Chonita 106.La Piedra 2da. Sección 107.Laguna de Cucuyulapa 108.Libertad 2da. Sección 109.Los Cerros 110.Mantilla 111.Marín 112.Miahuatlán (San Gregorio) 113.Miahuatlán (San Nicolás) 114.Miahuatlán 1ra. Sección 115.Monterrey 116.Morelos Piedra 3ra. Sección 117.Once de Febrero (Campo Bellota) 118.Pechucalco 2da. Sección (Las Cruces) 119.Rancho Nuevo 120.San Pedro Cumuapa 121.Yoloxóchitl 3ra. Sección Huimanguillo 122.Benito Juárez 1ra. Sección 123.Benito Juárez 2da. Sección (Monte Alegre) 124.Blasillo 1ra. Sección (Nicolás Bravo) 125.Blasillo 4ta. Sección 126.Huapacal 2da. Sección 127.Paso de la Mina 1ra. Sección 128.Pejelagartero 1ra. Sección (Gpe. Victoria) 129.Pejelagartero 2da. Sección 130.Pejelagartero 2da. Sección (Nueva Reforma) 131.Tres Bocas 1ra. Sección 132.Tres Bocas 2da. Sección (El Zapotal) 133.Zanapa 1ra. Sección Jalpa de Méndez 134.Ayapa 135.Benito Juárez 2da. Sección 136.Boquiapa 137.Chacalapa 1ra. Sección 138.Chacalapa 2da. Sección (San Manuel) 139.Hermenegildo Galeana 1ra. Sección 140.Hermenegildo Galeana 2da. Sección 141.Huapacal 1ra. Sección 142.Huapacal 2da. Sección (Punta Brava) 143.Iquinuapa 144.La Ceiba 145.La Cruz 146.Mecoacán 147.Mecoacán 2da. Sección (San Lorenzo) 148.Nabor Cornelio Álvarez 149.Nicolás Bravo 150.Reforma 1ra. Sección 151.Reforma 3ra. Sección (El Guano) 152.San Nicolás 153.Santuario 2da. Sección 154.Soyataco 155.Tierra Adentro 2da. Sección 156.Vicente Guerrero 1ra. Sección 157.Vicente Guerrero 2da. Sección 52 Sustainability 2019, 11, 1978 15 of 18 Table A1. Cont. Municipality Id Number and Locality Showed in Figure 3 Jonuta 158.El Cocal 159.Francisco J. Mújica 160.Jonuta 161.José María Pino Suárez (San Pedro) 162.La Bendición (La Tijera) 163.La Candelaria 164.La Concordia 165.Prudencio López Arias 166.Ribera Baja 2da. Sección (Gran Poder) 167.Torno de la Bola 168.Monte Grande Nacajuca 169.Arroyo 170.Cantemoc 1ra. Sección 171.Cantemoc 2da. Sección 172.Chicozapote 173.Corriente 1ra. Sección 174.Corriente 2da. Sección 175.El Cometa 176.El Zapote 177.Guatacalca 178.La Loma 179.Libertad 180.Lomitas 181.San Isidro 1ra. Sección 182.Taxco 183.Tecoluta 1ra. Sección 184.Belén 185.Chicozapote 186.El Chiflón 187.El Pastal 188.El Sitio 189.El Tigre 190.Guatacalca (Guatacalca 1ra. Sección) 191.Guaytalpa 192.Isla Guadalupe 193.La Cruz de Olcuatitán 194.Mazateupa 195.Olcuatitán 196.Oxiacaque 197.Saloya 1ra. Sección 198.San Isidro 2da. Sección 199.San José Pajonal 200.San Simón 201.Tapotzingo 202.Tecoluta 2da. Sección 203.Tucta References 1. Bruinsma, J. World Agriculture: Towards 2015/2030, An FAO Perspective; Earthscan and FAO: London, UK; Rome, Italy, 2003; p. 432. 2. FAO. Boletín de Agricultura Familiar Para América Latina y el Caribe. Alimentar al Mundo sin Comprometer el Future; FAO: Rome, Italy, 2018; p. 30. 3. Zedler, J.B.; Kercher, S. Causes and consequences of invasive plants in wetlands: Opportunities, opportunists, and outcomes. CRC Crit. Rev. Plant Sci. 2004, 23, 431–452. 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Parry, M.; Parry, M.L.; Canziani, O.; Palutikof, J.; Van der Linden, P.; Hanson, C. Climate Change 2007-Impacts, Adaptation and Vulnerability: Working Group II Contribution to the Fourth Assessment Report of the IPCC; Cambridge University Press: Cambridge, UK, 2007; p. 976. © 2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). 56 CAPÍTULO II HUMAN LIVELIHOODS AND WETLANDS CONSERVATION IMPROVED FOR THE TRADITIONAL MANAGEMENT AND USE OF THE MEJÉN MAIZE IN THE MARCEÑO AGROECOSYSTEM, IN TABASCO, MEXICO 57 Human livelihoods and wetlands conservation improved for the traditional management and use of the mején maize in the marceño agroecosystem, in Tabasco, Mexico Humberto Peraza-Villarreal1,2, Stephen R. Gliessman3, Alejandro Casas4, Roberto Lindig-Cisneros5 and Alma Orozco-Segovia1* 1 Laboratorio de Ecología Fisiológica, Instituto de Ecología, Universidad Nacional Autónoma de México; Mexico City, Mexico, hperazavillarreal@iecologia.unam.mx 2 Posgrado en Ciencias Biológicas, Universidad Nacional Autónoma de México; Mexico City, Mexico 3 Department of Environmental Studies, University of California, Santa Cruz and Community Agroecology Network, Professor Emeritus and Board Member, PO BOX 7653, Santa Cruz, CA, 95061-7653, USA, gliess@ucsc.edu 4 Laboratorio de Manejo y Evolución de Recursos Genéticos, Instituto de Investigaciones en Ecosistemas y Sustentabilidad, Universidad Nacional Autónoma de México, Campus Morelia, Morelia, Michoacán, Mexico, acasas@cieco.unam.mx 5 Laboratorio de Restauración Ambiental, Instituto de Investigaciones en Ecosistemas y Sustentabilidad, Universidad Nacional Autónoma de México, Campus Morelia, Morelia, Michoacán, Mexico, rlindig@cieco.unam.mx * Correspondence: aorozco@ecologia.unam.mx; Tel.: +5255-5622-9008 Received: ______; Accepted: ______; Published: ______ 58 Abstract In the alluvial plain of the state of Tabasco, the traditional Marceño agroecosystem is practiced in 203 rural yokot'anob and mestizo communities closely linked to the hydrological cycles of the region and the popal vegetation. This agroecosystem is associated with the cultivation of native maize mején that begins in the dry season (March-June) making use of the nutrient and humidity cycle of swamp soils. In this research, the current cultural practices of marceño management, attributes of maize mején, selection criteria, yield and morphological diversity of this maize were characterized through ethnographic work, questionnaires, semi-structured interviews as well as field evaluations and analysis of the information. Also, an inventory of the vegetation associated with the agroecosystem was carried out, the physical-chemical characteristics of the soil and water of swamp plots (6–8 months of flooding, plots S) and flooding plots (15–30 days of flooding, plots F). We found five important attributes that have allowed the in situ conservation of maize mején: the flavor of the dough, the ease of shelling, the diameter of the cob, the short cycle and the yield of the cob. Based on morphological data from 36 cob accessions, we identified an important diversity of maize mején. The height of the cob in the mején plant is a relevant morphological attribute since it allows harvesting even with flooding. The cultural management of the vegetation associated with popal and maize fodder improves the physical-chemical properties, providing organic matter and humidity, which allows good yields of maize mején grain obtained in plots F and S (3.3 to 4 Mg ha-1). The marceño favors the conservation of the flora and fauna of the wetlands since 206 species of aquatic and flood-tolerant plants were found in plots S and F. The marceño allows the adaptation of this productive system to the regional hydrological cycle, it is highly productive and favors the maintenance of the resilience of wetlands, in addition to providing important ecosystem services, as a refuge for 59 flora and fauna. It is a reserve of food, water and forest resources that exemplifies the agroecological management of the natural environment without drastically altering natural processes. Key words: landrace; mején maize; lowlands; popal; swamps; marceño agroecosystem Introduction Wetland conservation associated with cultural management is critical to reaching several of the sustainable development goals included in the United Nations 2030 Agenda, particularly those related to improving life on land and human livelihoods. Wetlands cover ⁓4–6% of the earth`s surface and include both permanent and seasonal coastal and inland natural and artificial water bodies (Zedler and Kercher, 2005; Mitsch and Gosselink, 2011; Ramsar, 2018). As these ecosystems provide approximately 40% of ecosystem services worldwide, including carbon storage, climate regulation, and flood protection, they are key to sustainable development (Zedler and Kercher, 2005). However, wetlands often are underestimated. It is estimated that, up to 87% of the world's wetland have been lost (Davidson, 2014; Costanza et al., 2016). Those remaining are threatened by anthropic factors, including deforestation, unsustainable intensive agricultural and livestock use, urbanization, dam construction, and fires (Davidson, 2014), resulting in eutrophication of water bodies, invasion by weeds, filling of wetlands, discharge of sediments, drying up of rivers, and interruption of their flow (Verhoeven and Setter, 2010; Jiang and Mitsch, 2021). These phenomena, as well as an increase in salinity due to influx of seawater contribute to reducing the ecosystem services wetlands provide (Millennium Ecosystem Assessment, 2005; Luan and Zhou, 2013; Ramsar Convention on Wetlands, 2018). As in other parts of the world, Mexico`s wetlands contribute 60 to the livelihoods of millions of people who have established agricultural systems within them. However, they are among the world`s most threatened ecosystems (McCartney et al., 2010; Verhoeven and Setter, 2010). Traditional agroecosystems in the Mexican state of Tabasco contribute to the resilience of wetlands. These agroecosystems represent an alternative that allows the resilience of these ecosystems and maintain a stable production of maize in the swamps, which might be possible to halt the deterioration and loss of wetlands. Maize cultivation in swamps of Tabasco may contribute to halting deterioration and loss of wetlands (Orozco-Segovia and Gliessman, 1979; Mariaca, 1993; Peraza-Villarreal et al., 2019). These millenary agroecosystems have demonstrated that ecological knowledge of highly productive sustainable wetland agroecosystems would face the socio-environmental changes occurring in these areas (Altieri, 1995; Erickson, 2006; Altieri et al., 2015). Wetlands under traditional agricultural management persist in several regions of the world, including the Hawyzeh marshes of Iraq and Iran (Arabs of the marshes) (Ichikawa, 2018), Lake Titicaca basin (waru-waru system) (Erickson and Candler, 1989), the Mexico`s Central Valley (chinampas system) (Rojas-Rabiela, 1993; González-Jácome, 2013), and flood-prone alluvial plains of Tabasco, Mexico (Orozco-Segovia and Gliessman, 1979). In the latter region, the marceño traditional maize agroecosystem has been developed in wetlands covered with popal (Thalia geniculata L.) (Orozco-Segovia and Gliessman, 1979). Maize is sown in areas previously flooded 10 to 100 cm deep for 3–7 months along the gradient of flooding resection (Orozco-Segovia and Vázquez-Yanes, 1980). Currently, this agroecosystem is maintained in 203 rural communities of the lower Grijalva-Mezcalapa river basin and the banks of the Usumacinta River (Peraza-Villarreal et al., 2019). 61 The high precipitation (1600–2000 mm) and low elevation (0–14 m a.s.l.) of Tabasco`s alluvial plane result in annual overflow of a network of tributaries (Peraza-Villarreal et al., 2019), due to the presence of large semi-permanent freshwater swamps originally covered with popal (Miranda and Hernández-Xolocotzi, 1963). For hundreds of years, the Chontal Maya (yoko'tan) population has developed a way of life closely linked to their wetland landscape, sustainably using multiple plant and animal resources (Peraza-Villarreal et al., 2019). During the prehispanic period, subsistence agriculture was likely related to the marceño agroecosystem (Vásquez-Dávila, 2001). The yoko'tan people have been described as an "amphibious culture" due to their ability to bioculturally manage periodic flooding. In the swamps, people fish and hunt wildlife such as turtles associated with wetlands, elaborate handicrafts with the swamp vegetation, practice the orchards, and raise of backyard animals. Furthermore, in the highlands they plant a maize-based polyculture twice yearly (milpa de año and tornamilpa), and in temporarily flooded swamps (bajiales) they cultivate the marceño agroecosystem (Vásquez-Dávila, 2001). The maize variety most often cultivated in the marceño agroecosystem is the native variety mején, from the Mayan mehen chakchob, which has a short maize (2½–3½ month) cycle or ixmején, ixtz'stz 'bacal (maize with thin "bone", or rachis) (Vásquez, 2008). Furthermore, the system includes beans, squash, cucumbers, and melons (Orozco-Segovia and Gliessman, 1979; Peraza-Villarreal et al., 2019). Upon cultivating mején in a marceño agroecosystem for the first time in an area previously containing popal, maize yield is estimated at 4.5–to 10 Mg ha–1 (Orozco-Segovia, 2016). Despite its high productivity, the practice of cultivating the marceño system decreased from the late 1950s-70s (Orozco-Segovia and Gliessman, 1979) as result of: 1) the Plan Chontalpa, implemented by the federal government in 1935- 62 1940 which drained over 60% of Tabasco`s lowlands (Tudela, 1989, 1990; Carabias, 1990); 2) damming of the Grijalva River, which modified the hydrological dynamics of the wetlands (Orozco-Segovia, 1999; Bueno et al., 2005; Peraza-Villarreal et al., 2019); and 3) accelerated urbanization of the lowlands, which required filling swamps and marshes (Zedler and Kercher, 2005). Due to that it is essential to promote conservation of wetlands and their ecosystem services, including food production. To evaluate the efficiency and productivity of the marceño agroecosystem, promote its use, and preserve the mején maize variety and related cultural knowledge. While the marceño system has been considered a sustainable agricultural method in flood-prone areas of Tabasco, it has been poorly / rarely been described (Orozco-Segovia and Vázquez-Yanes, 1980). Therefore, the objective of the present study was to characterize the marceño agroecosystem in rural communities vulnerable to cyclical floods in seven municipalities with low elevations in / in southern Tabasco (0–10 m a.s.l.) in which this system contributes a significant portion of maize cultivated for family-consumption / for local consumption. Study area The lowlands of Tabasco (physiographic province of the Coastal Plain of the Southern Gulf of Mexico) are located at the Tabasco State, in the southeast of Mexico, this region has alluvial origin and a mainly flat topography (0–50 m a.s.l in 90 % of the state) (INEGI, 2015; Peraza-Villarreal et al., 2019). The study site included the municipalities of Cárdenas, Centla, Comalcalco, Cunduacán, Jalpa de Méndez, Jonuta and Nacajuca. In Tabasco 70% are swampy areas and alluvial plains. The lowlands are formed with discharges of silty and clayey sediments carried for the water currents that descend from the Sierra Madre Oriental to the lower basin of the Grijalva-Mezcalapa and Usumacinta rivers; forming a complex 63 network of channels, which overflow during the rainy season (May-October) and Nortes (October-February, cold fronts) causing in large areas cyclic floodings for several months (CONABIO, 2019). The region presents a dry period (March-May) in which the water level drop and the marceño agroecosystem is practiced (CONABIO, 2019; Orozco-Segovia and Gliessman, 1979). The climate is Am (f), warm humid with abundant rains in summer, annual mean temperature is 26°C (García, 2004). Mean annual precipitation is 1,600–2,000 mm (SMN, 2005). In the region soils are mainly fluvisols, vertisols and gleyols; all of them with clayey texture with slow permeability, high organic matter (MO) content and high-water table (INEGI, 2017; Palma et al., 2017). In flood-prone areas vegetation is characterized for emergent hydrophytes, such as T. geniculata and Typha latifolia L. (popal and tular, respectively) (Orozco-Segovia and Gliessman, 1979). More than 55% of the state area is used for agriculture and livestock activities, mainly for cattle raising, 46% of the area is used for free grazing for ⁓1,600 million heads of cattle (INEGI, 2011; SIAP, 2017). Only ⁓10% is used to produce maize, cocoa and sugarcane (INEGI, 2011). 64 Figure 1. Location of the State of Tabasco, Mexico and of the studied municipalities in the area of distribution of popal and tular vegetation in the lowlands of Tabasco. Methods Vegetation associated to areas managed with the marceño agroecosystem In Comalcalco and Cunduacán from 2015 to 2017 we collected all the plant specimens in 12 plots under traditional marceño management. Six plots with cyclical floods of 6–8 months (swamps, S) and six plots with floods of 15–30 days (floodable areas, F). Plant collection was done in a zigzag pattern, inside each of 10 quadrats of 1 m2 separated one from the other 10 m (120 quadrats, three years in total = 360 m2). We also extended plant species collection to the remaining five municipalities, in which sampling was not systematic due to these municipalities being unsafe areas for people outside the community. The collected plants were identified based on comparison with herbarium specimens (Instituto de Biología 2020) and checked with the list of species from the lowlands of Tabasco (López-Jiménez, Jiménez-López, Castillo-Acosta, Gallardo-Cruz, and de Oca, 65 2020; Novelo-Retana, 2006; Orozco-Segovia and Gliessman, 1979), and southeast of Veracruz (Orozco Segovia and Lot, 1976) and the Interactive Flora of Mexican weeds (Vibrans and Tenorio-Lezama, 2009). Finally, to avoid synonymys in the scientific names were reviewed in http://www.theplantlist.org/, https://www.tropicos.org/home and http://www.worldfloraonline.org/. The habitat of plants was determined based on field data and a literature review. Physicochemical characterization of soil and flood water in plots managed with the marceño agroecosystem During the 2015 agricultural cycle, in S plots and F plots, each one of 1 m2, we took with a shovel five samples of 1 kg of soil from 0 to 20 cm in depth. A composite soil samples for each flooding condition were analyzed. The soil color was determined both wet and dry using the Munsenll color card. The textural class was determined by the Bouyoucos technique (AS-09 NOM-021-RECNAT-2000). Total C and N were determined with a Perkin Elmer 2400 series II elemental organic CHNS analyzer (Perkin Elmer Inc., Houston, TX, USA). Total K and Na were determined with a Corning 400 flame photometer (Corning Science Products, Corning, NY, USA); P available was determined with the Bray technique using ascorbic acid as a reducing agent. Total phosphorus content, the ammoniacal nitrogen (NH3-N), and the total nitrogen were determined with the methods 8190, 10023 and 10072 HACH, respectively, each parameter was measured in three water samples with the HACH DR 900 handheld colorimeter (HACH Co., Loveland, CO, USA). Determinations before sown of fresh and dry weight of organic matter and fodder of maize in S plots 66 We determined the plant material in two S plots, one covered by Cyperus articulatus L. and other by T. geniculata. In each plot we sampled three plants, cutting only the aerial part of these. The plant cover of each plant was 1 m2. At the end of the agricultural cycle, in each one of three S and three F plots, the fresh weight of 15 maize plants (fodder) was quantified in the field. After collection all plants were cut, air dried individually for 15 days and then placed in an oven at 100°C for 48 h. After that, the dry weight was determined. Characterization of the marceño agroecosystem To characterize the marceño agroecosystem and to know the criteria and attributes determining farmers preference, for mején maize, in relation to other varieties and hybrids, field trips were made during the 2014–2018 agriculture cycles, during these we applied to people an ethnographic method based on semi-structured interviews, questionnaires and participative field work (Appendix 1). This methodology was also applied to understand the ecological and social context linked to this agroecosystem. All interviewed accepted to participate in this process (local population, rural technicians, and authorities of the six municipalities, Cárdenas was not included. In total, 45 questionnaires, 30 interviews and 31 semi-structured interviews were conducted. We documented in the following order: the criteria of farmer selection of maize seeds for sown, the criteria and attributes determining farmers preference for mején maize, the traditional farmer pre-sowing seed treatments, the preparation of plots for maize sown, seedtime and agronomic characteristics of the agroecosystem, such as, seedtime, reseeding, traditional weed and pest control, soil fertilization, bending of the maize plant and harvest, and management of the harvest. After the sowing activities, the temperature of the fire for 67 weed control was measured with thermocouples K-type (Onset Computer Corporation, Pocasset, MA, USA) connected to data loggers (model U12-014, HOBO, Onset Computer Corporation, Pocasset, MA, USA. Some precise observations and additional methodological details are described beneath these lines. Criteria of farmer selection of maize seeds for seedtime To identify the criteria and attributes determining farmers preference for mején maize, we did a study case in Comalcalco, Tabasco. We observed how the farmers choose the best cobs between the cobs previously selected and stored at home for self-consumption. After that these cobs were shelled (removal of grains from the cob) and grains were stored to be used in the following agricultural cycle. From the selected cobs, we took 30 and measured: number of rows on the cob, rachis diameter and length at top, center and base of the cob, diameter at the center of the cob. Determination of yield of mején To determine the yield of mején maize we collected, from February to May in 2015 and 2016, 30 whole maize plants in each of 10 plots. We also recollected in 10 plots 525 cobs. Fresh and dry weight was determined in the whole plant. Also, it was determined the yield of grain of mején using the data obtained in the section “Morphological characteristics of maize mején cobs”. The yield was estimated using the following equation: GY = PD × CPP × GPC × WPG (1) 68 GY = grain yield, PD = Plant density (plants ha−1), CPP = Cobs per plant, GPM = Grains per cob and WPG = Weight per grain To determine the planting density in the marceño agroecosystem, we measured in 10 plots the distance between furrows, the distance between plants and the number of maize mején seeds placed inside each hole made with a sowing stick (macana); 30 measurements per data and per plot; planting density was calculated for hectare. Variability inside the maize mején and its management in the marceño agroecosystem Morphological characteristics of maize landraces cobs The characterization of the maize landraces managed in the marceño agroecosystem was done in the municipalities of Cárdenas, Comalcalco, Nacajuca, Cunduacan, Jalpa de Mendez, Jonuta and Centla; it was carried out in 40 plots under marceño management, in which cobs were randomly collected (N = 30–50 cobs for farmer plot). Cobs were carried to the laboratory, placed 24 h in desiccators and exposed to ether vapor to eliminate weevils, moths and bruchids. The cobs of each farmer were characterized based on the following morphological criteria for each cob: number of rows (NR); number of grains per each row (GR); height cob (HC) and diameters at the top (DTC), center (DCC) and base (DBC) of the cob; height of rachis(RH) and diameters of the rachis at the top (DRT), center (DRC) and base(DRB); seeds per cob (SC) and weight of these for each cob (GW); total cob weight (CW); grain color (Gc); number and color of husks. Measurements were carried out with a digital vernier. The facility of manual grain shelling, the pattern of grains in rows, grain form and weight of 1000 grains (1000GW) were also evaluated; for these 69 measurements we eliminated the seeds from the top and the cob base, as farmers usually do to select seeds for the next sown cycle. Kruskal-Wallis tests were applied to the cob’s variables from the different landraces and hybrids. Data of 30–50 cobs from each one of 35 farmers were analyzed with a principal component analysis (PCA). We included the following variables: diameter at center, top and base of the cobs, number of rows, number of grains in each row and total, pattern of rows, diameters at the base, center and top of the rachis. Morphological attributes of the full plant We collected randomly 30 maize plants in each one of four S plots, under marceño agroecosystem management. In the field and in the laboratory, in each plant we measured: plant height (from the base to the top, with and without tassel), leaves number and internodes, plant height at the cob location, number of cobs for plant, number of husks for cob, number of internodes in the peduncle, peduncle length and diameter; cob length; diameter at the stalk base; we also registered the grain and cob husks color. Additionally, we measured plant height and plant height at the cob location in 15 plants from each of four locations, in Centla, Cunduacán, Comalcalco, and Jonuta, municipalities). Results Vegetation in areas managed with the agroecosystem marceño In F and S plots 206 species were identified belonging to 69 families, for most of which one or two species were identified (Appendix 2, Figure. 2, Table 1). Those families with the greatest number of species were Malvaceae (11 species), Fabaceae (25 species), 70 Cyperaceae (17 species) Poaceae (15 species) and Araliaceae (8 species). Among them there were 142 herbs, 27 trees, 20 shrubs, 3 palms; the remaining 16 species were: lianas, climbers, creepers, and mistletoe. Aquatic plants included 60 emergent herbaceous plants, 15 free floating plants, 3 floating leaves plants, 3 submerged free-floating plants, 9 submerged plants, 4 riparian trees, 2 palms, 3 shrubs and 1 creeper. Forty species were found in literature associated with water bodies (water tolerant) and 63 were land plants, most of which were weeds that grow in crops or grasslands. 71 Figure 2. Total number of families and species of each of them found in the S and F plots. 72 Table 1. Habitat and life form and type of species collected in areas with S and F plots, both under agroecosystem marceño, in the seven municipalities where mején maize was collected. Habitat Life form Types Number of species Aquatic Creeper 3 Climber 1 Herb Emergent 59 Free floating 15 Free floating submerged 3 Floating leaves 2 Submerged 9 Palm 2 Shrub 3 Riparian Tree 4 Land Creeper 1 5 25 3 1 1 13 14 Climber Herb Lianas Mistletoe Palm Shrub Tree Riparian Tree 4 2 25 4 9 Tolerant Climber Herb Shrub Tree 73 Physicochemical characterization of soil and flood water in plots under marceño agroecosystem management Physicochemical characterization of soil and flood water showed high nutrients levels (Table 2 and 3, respectively). In the soil high values were found for total C and N, exchangeable cations and available P, while in flood water, high values were found for N, total phosphates, ammonium, phosphides and nitrates. While most farmers did not apply fertilizers, some used 50 kg ha–1 of urea salt. 74 Table 2. Physicochemical characterization of soil, in plots under marceño management in swamps (S plots) and flooded areas 15 days–1 month (F). Total percentage of C, N, exchangeable cations, available P, pH, texture and color soil. EC = electric conductivity. Mean values (SD). Plot type Exchangeable cations (cmol kg–1) pH water EC (ds/cm) % C total % N total Ca2+ Mg+ K+ Na+ Available P Bray (mg kg–1) F 6.7 (0) 0.4 (0.01) 1.95 (0.03) 0.21 (0.007) 27.33 (0.86) 12.59 (0.44) 0.505 (0.007) 0.25 (0.03) 14.04 (0.35) S 6.1 (0.007) 0.79 (0.01) 8.44 (0.05) 0.75 (0) 35.36 (3.79) 7.56 (0.92) 0.35 (0.06) 0.225 (0.007) 9.65 (0.35) Color Soil texture class Dry Wet Sand (%) Loam (%) Clay (%) Textural class F 10YR 7/3 10YR 4/3 2.62 45.28 52.1 Clay S 10YR 3/1 10YR 2/1 1.46 35.24 63.3 Clay 75 Table 3. Nutriments in the flood water in the swamp (S-plots). Mean values (SD). mg l–1 NO3-N NH3-N N total P total PO4 1.9 (1.74) 0.24 (0.16) 45.56 (6.89) 0.93 (0.61) 0.49 (0.39) Determination of organic matter in the marceño agroecosystem and fodder of maize in S and F plots (fresh weight and dry weight) before sown. T. geniculata had higher values of aerial organic matter in both dry and fresh weight than Cyperus articulatus. Organic matter coming from maize fodder had mean values between those of the two- swamp species (Table 4, Figure. 3). Table 4. Determination above the soil of fresh and dry matter of Cyperus articulates and T. geniculata. Three replications were evaluated, each one covering 1 m2. Data were extrapolated to hectares. Organic matter of fodder was determined in 45 maize plants of three S and three F plots. Mean value (±SD). Biomass weight (Mg ha–1) Species Fresh Dry Moisture (%) Thalia geniculata L. 123 (27.93) 19.6 (8.5) 84.8 (2.19) Cyperus articulatus L. 2.87 (0.51) 0.66 (0.08) 76.81 (3.26) Maize stubble S plots 7.5 - 10.4 (1.5) 6.8-9.4 (1.31) 9.0 (0.7) Maize stubble F plots 7.1-9.8 (1.41) 6.5- 9.04 (1.29) 8.5(1.04) 76 Figure 3. Vegetation patch of T. geniculata (a) and C. articulatus (b) sampled to determine fresh and dry weight. Characterizations of the marceño agroecosystem Criteria of farmer selection of maize seeds for sown Farmers who practice the marceño agroecosystem, select maize seeds for the next agricultural cycle, this is an activity carried out by both women and men. The larger cobs of the previous agricultural cycle are selected, and seeds are generally taken from the central part of the cob, although some farmers include seeds from the base of the cob. Grains from the top and base of cobs and grains from low quality cobs are used to feed backyard (solar o traspatio) birds, such as ducks, turkeys, different kinds of chickens, pijijes (Dendrocygna sp.), pigs and sheep. We observed that in base to the size of the cobs, covered by husks, farmers kept 25–30 kg of seeds. These seeds are used for sowing in the following agricultural cycle marceño or milpa de año, the last is harvested in September before the flood season, depending on precipitation. The grain is used for self-consumption, on average each family (3–4 individuals) daily consume ⁓1.5–2.5 kg of dough (⁓650 to 1,200 g of grain). Another part 77 of the grains is sold among the people of each town (*US$ 0.51–0.77 kg−1 (seed for sowing) and US$ 0.31 kg−1 (grain)) (exchange rate 1 USD = $19.45 MXN, 2017). In most of the cases observed, this selection occurred in the traditional barn of the farmer's house and not in the field. The selection criteria for the mején maize seed in the case study was based on 1) The flexibility of the cob due to the rachis (bacal) is thin and thus shelling is very easy. 2) The homogeneity of seed color (preference of white-yellow; blue and red grains are discarded; Table 5, Figure. 4). Currently, some farmers maintain, conserve and reproduce varieties of mején blue, red, yellow, for some ceremonies associated with the milpa Yoko'tan. 4) Finally, grains with embryos (corazón de la semilla) of dark color or damaged by weevil or moths are discarded. Table 5. Mean values (±SD) of attributes of mején maize selected by farmers from Villa Aldama, Comalcalco, Tabasco, to obtain seeds: Cob height (CH), number of rows (NR), central diameter cob (DCC), central diameter rachis (DRC) and grain color (Gc). N =32. CH (cm) NR (number) DCC (mm) DRC (mm) Gc 16.2 ± 1.4 10.8 ± 1.3 4 ± 0.4 2.1 ± 0.3 White-yellow Figure 4. Cobs of mején maize collected in Comalcalco, Tabasco, in 2014. Criteria and attributes determining farmers preference for mején maize 78 We observed that rural populations preferred maize mején or criollo, while in the populations close to urbanized areas (Villahermosa and Comalcalco) the native varieties of maize are unknown. The rooting of the Tabasco farmers for the mején maize cultivated in the popales is based on the attributes of mején, such as: flavor of the dough, grain yield, diameter of rachis, cob height on plant, grain color, ease of shelling, earliness, drought resistance, flood resistance and number of husks on cob (Figure. 5). Figure 5. Criteria and attributes of mején maize related to the rooting for their cultivation and percentage of the people interviewed who mention some of the attributes (N=32). Traditional farmer pre-sowing seed treatments Before sowing, the more traditional farmers of the region, soak maize seeds overnight (velación). Alternatively, seeds are hydrated under shade inside a wrap done with wide leaves from hoja de to (leaves of Calathea lutea (Aubl.) E.Mey. ex Schult) close to cocoa plantations, or Canna indica L., in areas close to water bodies, this system is locally called empuscaguado. Seeds can also be wrapped 79 with leaves of popal or cloth. After velation imbibed seeds are also enclosed in a wrap. In these conditions, the temperature inside the wraps was measured in three replications with a HOBO U12-013 (Onset Computer Corporation, Bourne, MA, USA) provided with a thermocouple TMC6-HD and an internal thermistor. The temperature outside the wraps done with hoja de to reached 27.1± 0.8 °C, while inside de wrap temperature was 27.8 ± 1.2°C. Germination was obtained in 24 h (radicle protrusion locally is known as seeds empitonadas). Some farmers place seeds eight days in this treatment to promote root development. Meanwhile, non-traditional farmers soak the seeds for 8 hours to impregnate them with insecticidal powdered (methyl) to prevent the embryo from being preyed upon by ants. Preparing the plots for maize sown To prepare the plots for sown in the swamp (flooded 8–6 months) or in floodable areas (flood lasts only 15 days–1 month), first open a pit manually in the center of the plot to have access to phreatic water in the dry season. The weeds and small shrubs are cut using a hook-shaped branch (garabato) and a machete. This activity is called chaponeo. Vegetation in the S plots was dominated by T. geniculata and Paspalum sp., Cyperus articulatus L. and Mimosa pigra. This work is carried out from the end of February to mid-March, as the level of the water table decreases. Some farmers carry out a first chaponeo when the soil is flooded 0.3–0.4 m above soil level, and a second chaponeo when the water table is –0.1 to –0.15 m beneath soil level. After the second chaponeo the organic matter (10–15 kg m–2 fresh mass or 1.3–2.6 kg m–2 dry mass of T. geniculata) forming a mulch that visually maintains the residual moisture of the swamp compared to the bare soil during the dry season. The more experienced swamp farmers cut the leaves stems of popal without removing the rhizome, which allows plant regeneration when the swamp is flooded. Some patches of popal are tolerated within the plots, due to their broad leaves are used as: mulch to protect the seedbeds (almácigos) for horticultural species cultivated in the marceño cycle. Popal leaves are 80 also used to wrap tamales, as forage for backyard poultry or to maintain fresh the harvested creole parsley (Eryngium foetidum, cilantro de Tabasco or cilantro de la tierra), util they are sold in local markets. After the second chaponeo weeds are left on the soil 2–3 days before the maize be sown. If a large amount of popal leaves is left on the soil, they are allowed to dry 1–2 weeks before sowing maize. Alternatively, before or even after sowing, the mulch may be fire. Temperatures of flame were up to 306 °C on the soil surface and 25 °C at –0.06 m, (sowing depth of maize), such that sown seeds are not damaged. The traditional agricultural management of weeds in the swamp in some cases begins a year before, at the end of the marceño cycle (May–June), weeds are manually extracted exposing their roots, mainly in the case of Poaceae, this procedure eliminates and incorporate weeds organic matter to the soil after their decomposition during flood and reduce weeds resprout. Seedtime and agronomic characteristics of the agroecosystem Seedtime occurs as the flood resection advances in the field, due to that it has been called the cornfield that walks (la milpa que camina, anonymous). Due to that, sown dates vary according to the topography of the plots. In general, during the nortes (cold fronts), S plots remained flooded (1–1.6 m above soil level) and dry in March–June, the water table decreased –0.5 to –3 m below soil level (in F plots). Agricultural calendar for marceño is shown in Table 6. 81 Table 6. Marceño agricultural calendar in S plots and description of activities. Month Activity Purpose Action Season February-March First cutting of popal and associated vegetation To eliminate and incorporate plants to soil when the water table is 10–20 cm above the soil surface and to promote decomposition of organic matter and contribute to soil fertility Cut down with machete and/eventually burning Start of dry season March Second cutting It is offered a traditional Chontal Maya ceremony to the crop To remove and incorporate vegetation remaining after cutting, into the soil and dry it exposed to sunlight. Organic matter is left on the soil surface as a mulch to maintain residual soil moisture. When the organic matter loses moisture, the plot may be burned to clean it from harmful fauna and search for chelonian Cutting with machete Dry Excavation of a craft well in the plot To make water available for irrigating horticultural seedlings in the plot Manually excavate well with drill shovel 82 Seedlings and seeds of horticultural species are planted or sown in the plot To cultivate vegetables for self-consumption and sale in local markets Manually sow seeds and plant seedlings Preparation of maize, cucumber, and squash seeds for sown To cultivate vegetables for self-consumption and sale in local markets Manually dig holes with macana and sown seeds Second maize sown To reseed where maize failed to sprout, or was damaged by birds, rodents, or ants. Additionally, maize is planted in previously flooded areas as flooding decreases Manually dig holes with macana and sow seeds and plant seedlings First weed control Control of the weed growth Cut weeds with machete or occasionally with herbicide using backpack sprayer 83 First pest control To eliminate insect pests such as armyworm (gusano cogollero) Spray insecticide using backpack sprayer Second weed control To control weed growth Cut weeds with machete and/or herbicide using backpack sprayer Second pest control To eliminate insect pests such as armyworm (gusano cogollero) Spray insecticide using backpack sprayer April Protection against animal pests To protect from birds and mammals that eat the crops Using film tapes or rarely slingshot with clay pellets as projectiles Avoid cultivated plants drought Maize and vegetables are irrigated if the drought and high temperatures are prolonged Using well water from the craft May First harvest of tender maize (elote) To provide tender maize for self-consumption and sale in local markets Manual harvest tender maize 84 Building of temporary camp to protect the maize plots To prevent theft at night Temporary camp with family groups and neighbors June Bending of maize stalk To accelerate maturation of cobs and protect them from birds and rain Cut and bend maize stalks with machete End of dry season Beginning of rainy season Maize harvest The cobs are harvested in sacks Harvest maize manually and haul it in sacks to move them by horse or traditional canoe (cayuco) or over the farmer shoulders. June to February or March Vegetation recovery Stop agricultural activities The plot is flooded Rainy season, 85 Generally, maize is sown in mid-March or even at the end of February depending on the rainfall occurring in the last rainy season. To avoid high midday temperatures, farmers generally begin to sow 5–6 a.m., and continue in the late afternoon. Holes for planting are traditionally made with ~1.8 m high digging stick (macana) made of a macuili (Tabebuia rosea (Bertol.) DC.) or tatúan (Colubrina arborescens (Mill.) Sarg.) sapling ~5 cm in diameter with a narrow or metal tip. A distance of 0.91 ± 0.11 m is generally left between furrows; sowing a complete furrow is referred as lucha. Within the furrows, holes are dug one step (87 ± 3.8 cm) apart, and 3–5 seeds are placed in each hole so that grown plants will support each other and resist the wind. Mean sowing density was 43,239 plants ha–1, and in each hole a mean of 3.9 seeds were sown. To sow a hectare, 12.5 kg of seeds are required (interval 3–5). (Table 7). Table 7. Agronomic characteristics of the agroecosystem marceño. Mean values (± SD). Distance (m) ha–1 Plot Plants Furrows Seeds sown in each hole Numbe r of furrows Plants for furrows Plant density Seeds (kg) S 0.94 (0.13) 1.04 (0.14) 3.8 (0.7) 90 380 34,339 9.927 S 0.95(0.11) 0.85 (0.10) 3.8 (1.3) 111 375 41,710 12.058 F 0.85(0.15) 0.84 (0.11) 4 (1.1) 112 442 49,501 14.310 F 0.7 (0.1) 1.1(0.1) 4.2 (0.8) 88 541 47,404 13.704 Mean 0.87 0.95 3.9 106.64 462.54 43,239 12.500 Production in the milpa (marceño agroecosystem) is diversified with other crops such as, creole parsley (Eryngium foetidum L., Apiaceae), squash (Cucurbita argyrosperma Huber), cucumber (Cucumis sativus L.), melon (Cucumis melo L.), watermelon (Citrullus lanatus (Thunb) Matsum and Nakai), 86 chilacayote (Cucurbita ficifolia Bouch), frijol pelón (Vigna unguiculata L. Walp.) and black bean (Phaseolus vulgaris L) which are sown alternated between the furrows of maize. Yuca (Manihot esculenta Crantz,) may also be sown in the borders of the F plots. In some cases, these species are sown interspersed with creole parsley, to ensure soil moisture this species required to be shaded, mainly by popal patches and to be in the lowest part of the plot, which cultivation has a 60-day growth cycle. To sow a hectare, 12.5 kg of seeds are required. The farmer reviews the emergence of maize plumules seven days after sowing, making the decision to reseed areas Furthermore, new areas of the plot are cleared for planting mején or criollo maize, as well as crops such as squash, cucumber, muskmelon, watermelon, and creole parsley. Reseeding is carried out once or twice more, until the entire plot is sown. Traditional weed and pest control Weed control in the marceño agroecosystem is carried out using a machete 7 and 15 days after the maize seedlings have emerged. In the swamp, the stubble of cut vegetation is incorporated into the soil, providing mulch which retards weed growth. Additionally, depending on the farmers` economic situation, synthetic herbicides may be used. Insecticides may also be applied 15 and 30 days after sowing. In tropical areas (Spodoptera frugiperda) is the main insect pest present in maize crops. Bending of the maize plant and harvest At the end of the grain filling, plants are bent to prevent cob damage by birds, such as parrots, cheche (Amazona albifrons), etc., and to prevent the cob from rotting due to infiltration of rainwater. The maize stalk is struck with the blunt side of a machete and bent a few centimeters below the cob, and the plant left 15 days to dry out before harvesting cobs; a yellowish color of the husks indicates high- quality dry grain. The harvest is kept in 80 kg henequen fiber sacks or in 50 kg nylon sacks. Management of the harvest 87 Traditionally, maize and pelón beans are dried principally during the waning moon to prevent attack by weevils (Prostephanus sp. and Sitophattackingais); maize cobs are dried in the husk. After 3 or 4 days, cobs are stored stacked in lofts (tapancos) or rustic barns or hung by bunch (mano = five large cobs, ⁓0. 85 kg) above the rustic stove (fogón), as the smoke protects them from weevils. Creole pumpkin seeds selected for later planting are set out to dry in the sun 2-4 days, and then wrapped in newspaper, or in popal or in hoja de to. The cobs are shelled with the tip of a machete, which is cut and conditioned for this purpose, or by hand, since the grains come off easily (Table 6). The husks are used to wrap local food as: tamales of chipilín (Crotalaria longirostrata) and chanchamitos (small tamales seasoned with achiote- Bixa orellana L. (1753)). Harvest Grain yield in S plots (3.4 ± 0.6 Mg ha−1) was significantly higher to the grain yield in F plots (3.2 ± 0.6 Mg ha−1) (F =4.79, GL = 1, 191, P = 0.029 (Figure. 6). 88 Figure 6. Grain yield in plants growing in plots with cyclical floods of 3–6 months (S plots) or 15-30 days (floodable plots, F plots) for the agricultural cycle (May-August) 2015. Variability inside the maize mején and its management in the marceño agroecosystem Farmers mostly plant the landraces locally identified as mején and criollo in the marceño agroecosystem. Upon losing native maize varieties due to flooding or drought, some farmers use hybrid VS-536 maize seed, without intermixing them with the landraces. Morphological characteristics of maize landraces cobs The morphological characteristics of 580 cobs from 36 maize accessions of 7 municipalities of Tabasco, Mexico were evaluated (Table 8). These cobs had been planted under marceño management in S plots and F plots. The maize landrace most frequently sown in the 7 municipalities was found to be mején (20 accessions), followed by criollo (14 accessions), and only two accessions of VS-536. Cob characteristics One-way ANOVAs results were shown in Appendix 3. With respect to 13 of the 14 characteristics of the cobs evaluated, significant differences were found between mején, criollo, and hybrid maize. However, 1000GW, no significant differences were found among varieties. For the remaining characteristics evaluated, the hybrid had the highest value, except for diameter at top of rachis, for which the criollo maize had the highest value and no significant differences were found between mején and the hybrid. Generally, mején had the lowest values, except for rachis weight (RW) and rachis height (RH), for which the criollo maize had the lowest values. For diameter of top cob (DTC) and the ratio between cob weight and rachis weight (CW:RW) no significant differences were found between mején and criollo. (Table 8). 89 Table 8. Morphological characteristics evaluated for 580 cobs collected from S and F plots in 7 municipalities of Tabasco: municipality and cob collection, maize variety, cob weight (CW), diameter of top cob (DTC), center (DCC) and base (DBC), height cob (HC), number of rows (NR), seeds per cob (SC), rachis weight (RW), rachis height (RH) diameter of rachis top (DRT), diameter of rachis center (DRC) and diameter of rachis base (DRB), ratio cob weight: rachis weight (CW:RW), grain weight per cob (GW), and 1000 grains weight (1000GW). Variety mején (M), variety criollo (C) and hybrid (VS). Farmer identity is indicated with a number and municipalities as follows: Cárdenas (Ca), Centla (Ce), Comalcalco (Co), Cunduacán (Cu), Jalpa de Méndez (JM), Jonuta (Jo) and Nacajuca (Na). Municipality Cárdenas Centla Comalcalco Cunduacán Variety mején mején mején mején mején criollo mején mején mején criollo mején criollo mején mején mején mején mején Farmer M6Ca M5Ca M2Ce M1Ce M3Ce C6Co M8Co M7Co M5Co C1Co M3Co C1Cu M5Cu M3Cu M1Cu M1Cu M2Cu Cob characteristic DBC (cm) Mean 0.43 0.46 0.39 0.37 0.39 0.41 0.33 0.41 0.41 0.41 0.41 0.48 0.41 0.35 0.37 0.38 0.42 SD 0.04 0.04 0.04 0.04 0.04 0.03 0.03 0.03 0.02 0.05 0.04 0.03 0.02 0.04 0.02 0.03 0.06 DCC (cm) Mean 0.42 0.44 0.42 0.40 0.42 0.39 0.36 0.39 0.41 0.43 0.40 0.45 0.39 0.37 0.41 0.38 0.41 SD 0.03 0.04 0.02 0.02 0.02 0.01 0.03 0.04 0.02 0.05 0.04 0.04 0.03 0.03 0.02 0.02 0.05 DTC (cm) Mean 0.35 0.38 0.26 0.26 0.26 0.32 0.24 0.35 0.28 0.33 0.36 0.35 0.33 0.24 0.25 0.27 0.33 SD 0.05 0.04 0.04 0.04 0.02 0.05 0.03 0.04 0.05 0.05 0.03 0.05 0.03 0.04 0.03 0.03 0.04 HC (cm) Mean 15.77 15.40 15.15 15.67 15.95 17.22 15.62 15.08 17.69 16.29 14.93 13.25 14.55 16.15 16.60 15.55 16.69 SD 1.84 2.15 1.35 2.18 1.92 2.21 2.43 3.50 1.82 0.97 2.43 1.28 1.87 2.00 2.23 1.12 1.80 NR Mean 11.33 11.54 11.75 10.67 11.00 10.27 10.40 10.89 10.77 9.75 11.72 13.64 11.85 9.92 10.91 10.62 10.60 SD 1.49 1.81 1.77 2.07 1.07 1.85 1.26 1.62 1.01 1.28 1.61 2.62 1.66 1.66 1.38 1.50 1.90 SC Mean 459.67 431.77 436.63 392.33 440.67 426.60 434.10 410.31 492.15 373.00 387.47 473.91 442.00 427.46 468.45 460.69 420.20 SD 85.71 78.53 74.84 53.90 58.35 80.10 74.82 68.28 53.02 38.94 91.27 70.22 88.13 77.44 54.61 50.88 89.42 RH (cm) Mean 16.96 16.88 16.04 16.47 16.65 18.13 16.83 15.30 17.52 16.29 15.99 14.15 15.50 16.60 17.32 15.75 16.33 90 SD 1.65 1.98 1.39 1.85 1.80 1.61 1.85 1.45 1.33 0.97 2.32 1.11 1.79 2.44 2.04 1.22 1.40 RW (g) Mean 18.22 23.91 20.43 23.00 22.17 21.66 15.29 16.43 20.74 20.13 20.64 20.74 14.90 14.19 15.56 11.38 16.50 SD 4.85 8.04 4.70 3.41 4.58 3.67 4.24 3.63 4.05 3.09 6.93 4.62 3.45 3.15 3.86 1.33 5.10 DRB (cm) Mean 0.22 0.26 0.24 0.25 0.25 0.21 0.20 0.23 0.23 0.25 0.25 0.27 0.22 0.19 0.21 0.19 0.22 SD 0.03 0.04 0.03 0.02 0.02 0.02 0.02 0.03 0.03 0.02 0.04 0.03 0.02 0.02 0.03 0.01 0.03 DRC (cm) Mean 0.20 0.23 0.24 0.24 0.23 0.16 0.18 0.21 0.21 0.24 0.24 0.25 0.20 0.18 0.20 0.18 0.21 SD 0.03 0.03 0.02 0.02 0.02 0.02 0.02 0.03 0.02 0.05 0.03 0.03 0.02 0.03 0.02 0.01 0.03 DRT (cm) Mean 0.18 0.20 0.14 0.15 0.17 0.17 0.11 0.18 0.15 0.17 0.20 0.18 0.17 0.12 0.13 0.13 0.14 SD 0.02 0.03 0.03 0.02 0.01 0.05 0.02 0.03 0.02 0.01 0.03 0.02 0.03 0.01 0.03 0.02 0.02 GW (g) Mean 130.37 139.58 126.98 117.33 139.25 126.43 108.60 111.97 148.22 126.25 94.40 104.26 101.94 115.77 130.40 111.69 127.52 SD 24.76 28.26 15.45 8.87 22.29 26.60 23.21 23.33 18.21 16.65 30.42 16.88 17.08 18.15 19.53 13.89 30.78 1000GW Mean 0.29 0.33 0.30 0.30 0.32 0.30 0.25 0.28 0.30 0.34 0.24 0.22 0.23 0.28 0.28 0.24 0.30 SD 0.04 0.05 0.08 0.04 0.03 0.04 0.04 0.05 0.03 0.03 0.05 0.04 0.04 0.04 0.04 0.03 0.04 CW kg Mean 148.59 163.49 147.40 140.33 161.42 148.09 123.89 128.40 168.96 146.38 115.04 125.00 116.84 129.96 145.96 123.08 144.02 SD 26.92 34.05 16.79 11.20 25.62 27.14 24.87 24.99 20.31 19.31 35.51 18.58 17.80 19.07 21.12 13.09 34.14 CW:RW Mean 12.38 14.46 13.90 16.35 13.71 14.96 12.49 13.03 12.27 13.74 18.21 16.64 12.90 11.01 10.70 9.42 11.59 SD 3.04 3.05 2.93 1.74 1.73 3.18 3.36 2.78 1.90 1.04 4.33 3.55 2.96 2.31 2.45 2.03 2.98 Municipality Jonuta Jalpa de Méndez Nacajuca Comalcalco Jonuta Variety mején criollo criollo criollo mején criollo VS-536 VS536 Farmer M2Jon M1Jon C1JM C2JM M1Na C1Na VS536Co VS536Jon Cob trait DBC (cm) Mean 0.35 0.43 0.39 0.45 0.42 0.46 0.49 0.48 SD 0.02 0.04 0.05 0.04 0.06 0.05 0.04 0.05 DCC (cm) Mean 0.34 0.42 0.41 0.43 0.47 0.51 0.49 0.48 SD 0.02 0.03 0.03 0.03 0.02 0.03 0.04 0.05 DTC (cm) Mean 0.27 0.35 0.27 0.36 0.29 0.34 0.37 0.38 91 SD 0.04 0.03 0.04 0.03 0.04 0.04 0.04 0.03 HC (cm) Mean 14.75 18.09 15.50 17.03 17.50 16.42 20.21 19.03 SD 1.18 2.17 1.38 1.40 2.18 1.67 2.90 4.23 NR Mean 11.00 12.44 10.73 12.63 13.00 12.83 14.03 14.83 SD 2.00 1.62 1.22 1.20 1.63 1.34 2.08 1.80 SC Mean 435.50 542.78 409.20 513.44 552.69 462.50 545.10 524.17 SD 106.43 80.73 62.92 64.01 98.07 56.00 92.44 77.21 HR (cm) Mean 14.45 17.53 16.11 16.28 18.38 17.64 18.37 16.13 SD 1.90 2.12 1.31 1.35 1.90 1.44 2.89 1.84 CRW (g) Mean 9.98 20.93 20.87 15.68 30.08 32.08 36.80 29.45 SD 1.80 4.72 4.66 3.92 7.00 3.92 9.44 6.32 DBR (cm) Mean 0.19 0.23 0.26 0.24 0.28 0.32 0.30 0.29 SD 0.02 0.03 0.02 0.03 0.03 0.03 0.03 0.02 DCR (cm) Mean 0.18 0.23 0.24 0.22 0.27 0.30 0.29 0.28 SD 0.02 0.02 0.02 0.03 0.02 0.04 0.03 0.02 DTR (cm) Mean 0.14 0.15 1.57 0.15 0.16 0.20 0.22 0.21 SD 0.02 0.03 0.26 0.03 0.04 0.03 0.03 0.03 WG (g) Mean 57.68 135.43 115.47 135.65 170.02 162.99 157.89 128.99 SD 10.59 28.36 21.12 19.91 21.81 22.71 37.29 20.37 1000GW Mean 0.14 0.25 0.28 0.26 0.31 0.36 0.29 0.25 SD 0.05 0.04 0.03 0.03 0.04 0.05 0.06 0.03 WC kg Mean 67.65 156.36 136.34 151.33 200.11 195.08 194.69 158.44 SD 10.65 32.02 23.74 22.73 22.95 24.53 43.24 23.56 WC:WR Mean 14.99 13.41 15.39 10.32 15.11 16.56 19.10 18.64 SD 3.11 1.88 2.61 1.63 3.73 1.92 3.87 3.27 92 Principal component analysis.– PCA carried out to 13 variables of morphological characteristics of the cobs (see Table 8). The first component (PC1) explained 55% of variance and the second (CP2) explained 17.6%, resulting in a combined explanation of 78.6% of the total variation (Table 9). Based on the value of their vectors, the most important variables in CP1 were DBC, DCC, NR, CW, DRB, DRC and DRT, all of which were associated with maize morphology. The most important variables for PC2 were GC and GR, which allows for identifying those native populations with the highest grain yield components (Figure. 7). Table 9. Principal components analysis applied to 36 accessions of maize cobs collected from seven municipalities of the lowlands in Tabasco, Mexico; 13 variables (morphological characteristics) of the cobs were evaluated (see Table 8). Vectors for the first two principal components. Variable PC1 PC2 Cob weight (CW) 0.764 0.467 Diameters of the cob Base (DBC) 0.868 -0.203 Center (DCC) 0.965 Top (DTC) 0.594 -0.448 Number Rows per cob (NR) 0.854 0.0778 Grains per cob (GC) 0.533 0.701 Grains per row (GR) -0.274 0.889 Cob height (CH) 0.365 0.253 Rachis weight (WR) 0.911 -0.0646 Diameters of rachis Base (DRB) 0.917 -0.104 Center (DRC) 0.852 Top (DRT) 0.844 -0.361 93 Weight of grains per cob (GW) 0.445 0.577 Figure 7. Dispersion for 36 populations of maize from the lowlands of Tabasco based on components PC1 and 2PC2 of the Principal Components Analysis, built with 13 morphological attributes. Variety mején (M), variety criollo (C) and hybrid (VS). Farmer identity is indicated with a number and municipalities as follows: Cárdenas (Ca), Centla (Ce), Comalcalco (Co), Cunduacán (Cu), Jalpa de Méndez (JM), Jonuta (Jo) and Nacajuca (Na). Cluster analysis.– Those groups observed through the principal components analysis were consistent with those of the cluster analysis based on the data of all populations and variables evaluated (Tab. 8). Of the diversity of populations analyzed, the dendrogram allowed differentiating four groups using the 94 Ward method standardized by column (Figure. 8). One group included one hybrid (VS-536) and two criollo accessions collected from the municipalities of Nacajuca and Comalcalco. The other three groups included mején and criollo accessions. Figure 8. Dendrogram of the cluster analysis for 36 accessions of maize from seven municipalities of Tabasco, Mexico constructed using the Ward method standardized according to column distances derived from 13 morphological cob variables. Variety mején (M), variety criollo (C) and hybrid (VS). Farmer identity is indicated with a number and municipalities as follows: Cárdenas (Ca), Centla (Ce), Comalcalco (Co), Cunduacán (Cu), Jalpa de Méndez (JM), Jonuta (Jo) and Nacajuca (Na). 95 Morphological traits of the full plant A majority (80%) mején plants were taller than 2.75 m. In 53% of plants, the lowest cob was > 1.8 m above the soil surface (Figure. 9). Figure 9. Frequency of heights for full mején plants (including tassel) and height at which the first cob was located. Plants were sampled in S and F plots in the municipalities of Centla, Comalcalco, Cunduacán and Jonuta, Tabasco, Mexico. Mean plant height = 3.17 ± 0.23 m. Mean height at first cob = 1.88 ± 0.20 m. Comparison of costs of mechanized production in rainfed plots and the marceño agroecosystem 96 Production costs of the traditional marceño agroecosystem principally involving family labor and use the seed produced by the family, are lower than those of the marceño conventional that purchase the seeds produced by neighbors and use limited hired external labor, some agrochemicals use. Mechanized agriculture mainly uses hired labor, hybrid seeds and agrochemicals. Total costs = $94.75, $246.28 and $496.59 USD ha–1, respectively (Figure. 10, Appendix 4). Figure 10. Diagram present results about three maize productions strategies in Comalcalco municipalities: Traditional marceño agroecosystem involve family labor and seed produced by the family, marceño conventional use seeds produced by neighbors and limited hired external labor and some agrochemicals. Mechanized agriculture mainly uses hired labor, hybrid seeds and agrochemicals. Discussion 97 In the seven municipalities studied in Tabasco the marceño agroecosystem remains as a living biocultural knowledge. However, it is only for self-consumption, and it is only practiced in impoverished rural communities with strong cultural roots that have adapted to cyclic flooding. Soil and water in S and F plots were adequate for agriculture, as they were non-saline and had a neutral or slightly acidic pH which favor availability of essential nutrients for crops (Reddy et al. 2015; FAO 2023), which might explain the management and high productivity of the marceño agroecosystem. Mején maize and marceño agroecosystem In the marceño agroecosystem we mainly identified six characteristics that make it an model system for the use of wetlands and the cultivation of mején maize: 1) agricultural labor begins and ends when the land is still flooded and cultural activities and biological process related to maize culture might occurs in successive steps, as the recession of the flood progresses; 2) the variety of maize adapted to this agroecosystem, mején, has a short life cycle and morphological characteristics adapted to the dynamics of flooding in wetlands; 3) the marceño agroecosystem take advantage from the swamp soil nutrients and from residual waters, lixiviates and alluviums carried into the swamps through runoff and floodings; 4) the marceño agroecosystem favors the conservation of the flora and fauna typical of wetlands; 5) the marceño agroecosystem favors the in situ conservation the agrobiodiversity of the maize mején landrace; 6) This agroecosystem favors maintenance of the traditional knowledge associated with the wetlands and maize mején. Early start and long-term use Marceño agroecosystem could provide an option for cultivating in areas where the dry season prevents agriculture in non-floodable areas. Pre- and post- cultivation activities in the field 98 initiate close to the end of the rainy season (February-March) and end at the start of the following rainy season (June-July) when the water table of the swamp rises. This favors a complex, dynamic and creative agroecosystem. Below, we list their principal characteristics. a) Farmers initiated de marceño agroecosystem activities applying pre-germination treatments to maize seeds. One of them consisted of soaking overnight the maize seeds (velación) which has a deep ritual significance. The other had a practice value and prevents the loss of seeds and seedlings at the beginning of the dry season. In this case maize seeds were imbibed wrapped in leaves of broadleaf species, typically hoja de to and popal leaves, inside the wrap temperature increased around 1°C, water availability for imbibition was less than in soaking treatments and the root protrusion was accelerated in 24 h (seeds empitonadas). Alternatively, seeds are left in this treatment for up to eight days to promote the root development prior to sowing, this practice prevents seedling death in F plots if drought progresses faster than expected, allowing both a greater establishment success of the early germinated seedlings and seeds escape from predation by ants, rodents, and birds, such as, Quiscalus mexicanus (Icteridae). Wrapping the seeds may have a similar effect as pre-germination seed hydration-dehydration treatments – known as priming - used in commercial agriculture in many parts of the world (Halmer, 2004). b) Weed control initiates in February when the water table is 0.3 to 0.6 m above the soil surface, The first chaponeo provides organic matter for decomposition, while the second in soils with residual moisture accelerates decomposition of the organic matter previously deposited and its incorporation to the soil, as occurs in alternate cycles of wetting and drying of organic matter (Birch, 1960; McLatchey and Reddy, 1998). The second chaponeo also allows for maintaining soil moisture during the dry season and limiting weed growth. 99 c) Reseeding was an activity that replaced maize seeds or seedlings that died or were predated. d) In Tabasco “la milpa que camina” is a phalanx strategy, that is maize seed is sown as water recession advances Thus, in a single agricultural cycle it is possible to observe maize in different physiological stages. In Chiapas, Mexico the practice of the milpa que camina (milpa walking) – used to increase agricultural surface area– promotes rainforest deforestation (Blom, 1983). In the marceño agroecosystem the milpa ”walking” allows for obtaining maize for different culinary purposes - for example, tender maize for tamales as well as grain to be stored for long-term use. Harvests After 105 days, both S and F plots produced a maize yield greater than 3 Mg ha–1, which is significantly higher than that reported in Tabasco (1.7 Mg ha–1 – 1.84 Mg ha–1) during the study period (2016–2018; NFOSIAP 2023; SIAP 2023). Flood recession agriculture is also used in Vietnam`s Mekong delta; however, in this case rice is benefitted by flooding (flood based farming), providing 2.5–3 Mg ha–1 for family consumption. After rice cultivation they practice a flood recession commercial crop of maize (Fox, 2016). (Fox, 2016). In the present study, upon cultivating maize with a plant density common for landraces in Tabasco (43,000 plants ha–1; de la Cruz-Lázaro et al, 2009), farmers obtained 3.40 Mg ha–1 in S plots and 3.20 Mg ha–1 in F plots, like that reported by de la Cruz-Lázaro et al. (2009) using fertilizer for 9 tropical genotypes of maize (including two hybrids). In Cardenas, Tabasco, for the first incorporation of an undisturbed popal to the marceño agroecosystem management Orozco- Segovia and Gliessman (1979) report a yield of 4.5 Mg ha–1. While hybrid maize is commonly cultivated n F plots, due to recent flooding in Tabasco, farmers occasionally used these plots to 100 cultivate mején. Thus, some highlands which are briefly flooded may be converted to marceño agroecosystems. In dry years, some farmers take the risk of cultivating a second or third crop of mején or other variety depending on seed availability, mainly in areas where flooding usually lasts less time than in S plots. However, the third crop might result in crop failure. In the case that the beginning of the rainy season is correctly predicted, two crops may be obtained per year. Dry cobs are hauled using a cayuco (small canoe), horse, or by foot, walking waist-deep in swamp water. instead of waiting until the ears are dry, farmers may decide to harvest maize when it is tender (Mariaca, 1996; Orozco-Segovia and Gliessman, 1979; Peraza-Villarreal et al., 2019). When rains are late, cobs in their husks are dried in the sun on outdoor concrete surfaces. Methyl powder is occasionally applied to avoid predation by ants. Another advantage in S plots is cultivating a variety of horticultural species at the same time that maize. In the present study, it was difficult to measure the yield of these species as they are continually harvested. Maize mején have morphological characteristics adapted to the dynamics of floodings in wetlands The short life cycle and morphological characteristics of mején maize are adapted to the hydric dynamics of swamps and other flooded areas. Its 2½–3½ month growth cycle allows farmers to obtain 1–3 harvests per year of tender and grain of mején maize, depending on the timing of the flooding recession period. The hybrid VS-536 also has a relatively short (125 d) phenological cycle, but it has a height of 2.70-2.75 m, and the lowest cob is located at 1.10-1.47 m in height (Cruz-Lázaro, 2009; Zarco, 2023). While mején was 3.17 m ± 0.23 m in height and the lowest cob was highest on the plant (1.88 ± 0.20 m), which increases the chance of resisting flooding 101 and allows the grain to dry on the stalk and cobs to be harvested despite flooding. Although there is an associated risk of the wind bending the plant, the Interviewees also stated that if they cultivate several plants together, they can straighten them out, so they support each other if the wind bends them. For other seven maize genotypes and landraces from 71 accessions of Tabasco, mean height of plants (2.1 ± 0.23 or 2.69 m) and lowest cobs (at 0.9 ± 0.18 m or 1.1 m) has been found to be similar or lower to those of the hybrid VS-535 (Cruz-Lázaro, 2009; Guillén-de la Cruz et al., 2014). In non-floodable fields with use of fertilizer, lowest mején cobs at 1.41 m ± 0.02 in height (Aguirre-Rivera, 2019). Additionally, the large number of husks on the cob (9–13) protects them from high relative humidity and inhibits damage by birds and weevils during storage in the barn (trojes or tapancos). As a result of these attributes, farmers identify mején maize as being flood-resistant at the end of its cycle, when the grain has fully grown. However, it does not resist long periods of flooding in its early stages (only 3–5 d). On the other hand, farmers attribute also some drought tolerance to mején maize as - in the case of drought they are typically able to at least obtain a yield sufficient for family consumption. Marceño agroecosystem take advantage from soil nutrients, residual waters, lixiviates and alluviums carried to the swamps with flooding In addition to organic matter and the fodder of maize plant being deposited on the soil during chaponeo, S and F plots receive agricultural runoff from higher elevations, which carries sediments and nutrients from other crop fields. According to Ferat et al. (2020), in the Usumacinta River basin water quality exceeds the ecological standards stipulated by Mexico`s regulation CE-CCA-001/89 governing protection of aquatic life. This may be one of the reasons for absence or reduction in fertilizer use in the marceño agroecosystem. Additionally, in Tabasco, eutrophication has occurred in water bodies as a result of residual waters freely flowing into 102 water bodies and cisterns in areas where the groundwater table is high most of the year, as well as intensive use of fertilizer, which is distributed to mechanized farmers by the federal government. Such eutrophication is evidenced by high levels of Ntotal (45.56 mg l–1), NO3-N (1.9 mg l–1) and Ptotal available (0.93 mg l–1) found in swamp water (Table 3); while in soils of S and F plots values were 0.75% and 0.21%, respectively; and P available 9.65 mg kg–1 and 14.04 mg kg–1; respectively. The N content of the S plots indicates that their soils are extremely rich, while that of the F plots indicates they are only moderately rich. However, based in Reddy et al. (2015) and FAO (2023) F plots had a greater available P than the S plots. Lumsden et al. (1990) also in Mexico, popal vegetation covers 0.15 million hectares (INEGI, 2011), including large swampy areas and shallow waters in Tabasco, southwestern Campeche, northern Chiapas, and southern Veracruz (Rzedowski, 1983). These regions are irrigated by the San Pedro, Usumacinta, Grijalva- Mezcalapa, Uxpanapa, Tonalá, and Coatzacoalcos Rivers, and a complex network of tributaries which carry sediments and wastewater to the popal patches and surrounding areas (Bueno et al., 2005; Orozco-Segovia and Vázquez-Yanes, 1980). The more traditional farmers consciously maintain fragments of popal in their agricultural land to protect horticultural plants and avoid cutting popal rhizomes to promote resprouting. However, each cutting of popal drastically reduces its aerial biomass. The total C content was moderate (8.4 %) in S plots that might be associated to the chaponeos previous and at the beginning of cultivation (Table 4). Meanwhile, the 1.95% C content of the F plots is very low, likely because they principally consist of agricultural land where wild plants are limited to weeds. The relatively low C content of the swamp soils may be related to loss of popal and/or reduction and fragmentation of wetlands (Díaz-Perera, 2014). Stored carbon levels have been reported for popal 103 and tular to be 169.63 and 88.4 Mg ha–1, respectively (De Jong, n.d.; Pellat, Espinoza, Gaistardo, Etchevers, and Ben, 2016). Free grazing cattle raising in flooding areas also destroy the structure of soils (Rodriguez-Medina and Moreno-Casasola 2017). In tabasco, a larger surface area is devoted to cattle-raising than to agricultural crops. Most extensive cattle-raising in swampy areas consists of the zebu breed for meat production or to reproduce herds (López-Hernández et al. 1997). In soils compacted by cattle, high levels of stored carbon may improve the physiochemical properties of soils - particularly soil cation exchange and soil moisture retention, and contributes to the stability of clayish soils, such as those found in swamps (Table 2), as carbon improves soil structure by agglutinating particles forming aggregates (FAO, 2023). The abundance of popal decreases also using fire, it is gradually substituted for Typha, Scirpus, Cyperus, Phragmites and Cladium whose rhizomes turn gradually the wetlands in inadequate areas for marceño agroecosystem (Alma Orozco Segovia personal observations). Nevertheless, Plant communities such as tular (Thypha) or carrizales (Scirpus, Cyperus, Phragmites and Cladium) and popales (T. geniculata) reaches very high values of organic matter up to 75 Mg ha– 1 to 90 Mg ha–1 per year, and where the released minerals are exported to lower areas until they reach the coastal lagoons and subsequently the sea or are used locally and immediately by a wide number of species (Ruvalcaba, 1979). The present study found that the two most common aquatic plants in the marceño agroecosystem in Nacajuca, Tabasco - Cyperus articulatus and T. geniculata - have an aerial / above-ground fresh mass of 2.87 Mg ha–1 (±SD = 0.51 Mg ha–1) and 123 Mg ha-1 (±SD = 27.93 Mg ha–1), respectively, while, dry mass of these two plants was 0.66 Mg ha–1 (±SD = 0.08) and 19.6 Mg ha– 104 1 (±SD = 8.5 Mg ha–1) respectively, which indicated the organic matter incorporated into the soil, the water content in each species, and explained the residual moisture that T. geniculata maintains on the soil after it is cut in S plots. Thalia geniculata is useful as mulch, when applied humid it is harmful to seedlings given a temperature increase during evaporation. Cyperus articulatus and other Cyperaceae are secondary aquatic plants that appear after T. geniculata has repeatedly been cut (Orozco Segovia and Lot, 1976). Gliessman (1998) reported that systematic annual incorporation of popal into undisturbed soil may result in formation of soil consisting of more than 30% organic matter, with total nitrogen values of up to 3%. In the marceño agroecosystem, organic matter is produced and deposited in situ during chaponeo (clearing), while in the chinampa agroecosystem of the Valley of Mexico, aquatic vegetation (Eichhomia crassipes and Nymphaea mexicana) is collected and added to the surface as fertilizer (Quiroz, Miranda, and Lot, 1982). In other areas of the world - including China, Vietnam, and South America the aquatic free-floating Azolla spp. (associated with Anabana azollaea) is favored and cultivated to provide N to rice crops in China and Vietnam (Nam and Yoon, 2008; Thapa and Poudel, 2021). Azolla may be produced in situ or added to the crop. Traditional wetland rice cultivation in these regions has been extremely sustainable because the biological N2 fixation in Azolla has allowed for maintaining moderate but stable rice yields for thousands of years without applying additional N and without harming the environment (Ramsar Convention on Wetlands, 2018). While Azolla is common in Tabasco, in the marceño agroecosystem it is not managed as fertilizer, but rather merely naturally deposited and incorporated into soil during the dry season. The role of the marceño agroecosystem in favoring in situ conservation of the mején landrace 105 The morphological differences among the 36 cobs accessions observed in the principal components analysis and cluster analysis indicate the diversity of the accessions, as well as the level of variation of the variables. Several authors have pointed out that native maize has morphological variability which may be attributed to the seed selection process carried out by farmers based on the characteristics of their interest. In the present study, the attributes were mainly related to grain color, rachis diameter, and ease of shelling. The cluster analysis indicates two groups: group I comprised of mején-criollo maize, and group II comprised of hybrid VS-536 maize and two accessions of criollo cobs from Nacajuca and Comalcalco was possible thanks to the degree of crossing between mején and hybrid maize. The population of the rural communities of the lowlands of Tabasco prefer mején maize, which has contributed to the conservation of this variety (tuxpeño and olotillo landraces). As a result of farmer interviews, we distinguished 8 attributes for which rural communities had selected mején: precocity, grain yield, number of husks, flood tolerance, and drought tolerance - which were discussed above, as well as number and weight of grains, flavor, ease of shelling, and grain color. Our results showed a lower rachis/total cob ratio of 13.45 for mején than 18.96 for VS-536, which makes the process of manually shelling the grain easy. This attribute is also related to ease of husk elimination. Due to that the low rachis/total cob weight ratio and the mején rachis are morphological traits that farmers associate with grain yield and is prioritized during seed selection. Rachis diameter of mején maize was ~4.01 ± 0.35 cm and that of hybrid maize ~ 4.5 ± 0.3 cm. Another attribute of mején evaluated was flavor for elaboration of chorote or pozol, a cold drink made of maize dough with roasted cocoa beans. Tender mején maize also resulted in dough ideal for producing seasonal/daily local foods such as thick tortillas, ziguas, tortilla chips, totopostes, maneas, several types of tamales including those made with tender maize, and pinole 106 (cold roasted corn drink),. One study demonstrated that the texture of mején dough has the lowest values for strength and cutting and produces the most highly appreciated tortillas (Jiménez- Juárez, 2012). The marceño agroecosystem favors the conservation of wildlife The marceño agroecosystem favors conservation of wetland flora and fauna, S and F plots contained 101 hydrophytes and 44 species tolerant to flooding, which were mainly collected in Centla, Comalcalco, Cunduacán, Jalpa de Méndez, and Nacajuca. Four species are mentioned in the Mexico regulation NOM 059 SEMARNAT-2010: the flood-tolerant tree Ormosia macrocalyx Ducke, the hydrophytes Pontederia azurea Sw and Eichhornia azurea (Sw.) Kunth, which are considered endangered species; and Bactris major Jacq. var. major (Bactris balanoidea (Oerst.) H. Wendl) which is a protected species (DOF, 2010). In Mexico, 240 hydrophytes have been reported, which are grouped into 62 families (Mora-Olivo, Villaseñor, and Martínez, 2013). The present study identified 101 aquatic species, 96 of which were found only in S plots, while 20 species were found in both S and F plots. However, only 36 of the aquatic species identified in the present study coincided shared with those cited by Mora-Olivo et al. (2013), which indicates the need for further study of Mexico`s aquatic flora. The present study identified 29.42% more aquatic plants than the vascular plants previously identified for the Centla Swamps Biosphere Reserve. Given the diversity of aquatic species of the wetlands in Tabasco, there is a need to implement programs to protect and preserve this biodiversity (Mora-Olivo et al., 2013). In S plots there were an apparent clear dominance of introduced cultivated grasses, we identified 8 introduced Poaceaes, which are mainly used as cattle fodder in open grazing areas. These grasses included the introduced species Cynodon dactylon, Cynodon plectostachyus, and 107 Panicum maximum Jacq., as well as the native invasive species Phragmites australis and Panicum hirsutum, which highly compete with other native wetland plant species when the impact of cattle is high (Rodriguez-Medina and Moreno-Casasola 2017). Stands of Phragmites australis and other Poaceae prevents agriculture due to massive development of rhizomes and runners, similarly to Typha spp. and other wetland species, which are favored by frequent grazing, cutting, and fire. The wetlands are burned to facilitate hunting, collection of wild fauna, and rat control. Propagation of P. australis is known to be favored by fire (Rodríguez-Arias, Gómez-Romero, Páramo-Pérez, and Lindig-Cisneros, 2018). Flood-tolerant species also invade disturbed wetlands. Invasion by Poaceae, Cyperaceae, and other flood-tolerant species initiates from the periphery of a wetland, expanding toward its center. Aquatic plants of other families rarely form pure stands in the area; except for T. geniculata and Saggitaria latifolia, they are combined with another hydrophytes (Rodriguez-Medina and Moreno-casasola, 2017). These two species also are severely damaged by grazing, cutting, and fire. Wetlands are used for agriculture, and provide habitat, shelter, food, and nesting material for a large number of local and migratory bird species (Valdez-Leal et al., 2018), fish, amphibians, reptiles, crustaceans, mammals, invertebrates, and countless other organisms, as insects in their larval stages, as well as plants used as substrate by epibiont species (mollusks, worms, termites, and protozoa; Bueno et al., 2005); some of which are incorporated into the daily diet of fish such as Dormitator maculatus (tópen), Atractosteteus tropicus (pejelagarto), Ophisthernon aenigmaticum (madre fil), and Cichlasoma urophtalmus; crustaceans such as Procambarus llamasi, and mollusks (Pomacea canaliculata). In the swamps, during the flood season, topén fish catching ~150 to 200 kg d–1, which is sold for $1.03-$3.08 USD per kilo, depending on its abundance. Since prehispanic times, local peasant-fisher families have made use of wetland 108 resources for family consumption and sale in local markets. Rural communities of the lowlands of Tabasco have a lifestyle and traditions rooted in the wetlands (López-Hernández et al., 1997; Mariaca, 1993; Moguel and Toledo, 1999; Reyes-Escutia and Barrasa-García, 2017). These ecosystems provide many environmental services which benefit the local communities, such as flood regulation, control of erosion and sedimentation, water supply and purification, and maintenance of fisheries (Verhoeven and Setter, 2010; Zedler and Kercher, 2005). The marceño agroecosystem contributes to maintaining wildlife diversity, because during the rainy season agriculture does not occur. Cultural values of mején maize The mején variety of maize is highly valued by the rural population of the region, it is used in religious rituals such as the enrame (Catholic festival celebrated in the city of Comalcalco and town of Cupilco), as well as in offerings to the dead and to saints. Also, agricultural products including maize, cocoa, and beef from the marshy fluvial plain are bartered for mangrove and marine products from the coastal plain such as mackerel (Caranx caninus), tarpon fish (Megalops Atlanticus), dogfish (Mustelus sp.), crab (Callcineta sapiduss), and oysters (Crassostrea virginica), as the saline coastal soils are not suitable for maize production (Humberto Peraza- Villarreal, personal observations). During mején sow, four maize seeds are sown per hole, which has ceremonial significance in the Mayan tradition. The marceño agroecosystem provides a model for ecological restoration and conservation of wetlands that have been altered through Tabasco`s biocultural landscape, which might allow for recovering ecosystem services of wetlands (Peraza-Villarreal et al., 2019). Conclusion 109 The marceño agroecosystem yields 3.5 to 4 Mg ha–1 of mején maize, which contributes to local food security. This yield is achieved with little or no synthetic fertilizer use, thanks to mineralization of swamp vegetation and harvest waste incorporated into the soil organic matter after flooding. In the case of maize stubble, the volume of dry organic matter incorporated into the soil depends on the planting density and whether some is used as livestock fodder. Meanwhile, so that maize may withstand the region`s dry season (March-June), the traditional practice of cutting down popal to generate mulch contributes to soil structure and prevents rapid evaporation of soil moisture, reducing hydric stress (Peraza-Villarreal et al., 2019). Mulch also acts as a physical barrier, controlling weeds during the early stages of the crop. Costs of production in S plots are lower than those of mechanized production at higher elevations (F plots). The yield of stubble biomass during the March-June 2016 crop season for a marceño agroecosystem was like that obtained for conventional production in F plots. Mején landrace is adapted to local conditions of high humidity, taking advantage of the residual humidity of swamp soil so that cobs may reach physiological maturity and be harvested before or during cyclical flooding. In this manner, farmers who continue to cultivate mején maize contribute to maize agrobiodiversity, and to maintaining viable the marceño and a food system adapted to local environmental changes and allow the evolution of mején maize, which has strong cultural roots, the farmer preference for mején maize has been the driving force for in situ conservation despite the introduction of hybrids to the region, either through agricultural development programs or the interest of some producers. 110 Acknowledgments We are grateful for the collaboration of the farmers of Comalcalco and Cunduácan. We are also grateful to the researchers: María Esther Sánchez Coronado, José Gerardo Rodríguez Tapia, Alejandro René González Ponce, José Miguel Baltazar Galvez and Dra. Luz Palestina Llamas Guzmán; for technical support. 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Do you practice any of these agricultural cycles? marceño ( ) (March planting) milpa de año ( ) (rainfed agriculture) tornamil o tornamilpa ( ) mila de sol ( ) seedtime harvest date Do you recognize these agricultural cycles? Where do you think is the best place to plant maize? Why? Variety name: variety attributes: early: ( ) pest resistance:( ) disease resistance:( ) flood resistance: ( ) drought resistance: ( ) wind resistance: ( ) flavor: ( ) color: ( ) facility of shelling: ( ) seed weight ( ) dough color: ( ) number of seeds ( ) yield ( ) type of rachis ( ) Other: 117 What does the name of the variety of maize mean? Why do you prefer to plant mején and no other varieties of maize? Can the mején be planted anywhere? Name of collector: Humberto Peraza Villarreal Date of collection: / / Number of accession: State: Tabasco Municipality: Comalcalco ( ) Cundoacan ( ) Community Locality: Slope: precipitation: temperature: latitude: longitude: elevation m snm: Name of the farmer: age: ethnicity: Collection site: 1-farmer's house ( ) 2-field (plot) ( ) 3-market ( ) 4-barn ( ) 5- institution ( ) 6- warehouse ( ) 7- other: Name of your plot: Surface: Number of cobs purchased: Number of grains: Number of accession: Variety used by the farmer ( ) How long have you been growing this maize variety? origin of the grain Introduced variety used ( ) How long have you been growing this introduced maize? origin of the grain Hybrids used ( ) How long have you been growing this maize hybrid? origin of the grain Uses of maize: pozol ( ) tortillas ( ) forage ( ) fuel ( ) medicinal ( ) tamal ( ) totopostles ( ) otro: Description of uses: Destination of production: self-consumption ( ) sale ( ) both ( ) Characteristics of the cobs Information of grains Form: longitud cm: color: grosor mm: Number of rows: diámetro cm: textura: ancho/long: Grains in each row: diámetro/ longitud: ancho mm: grosor/ancho: Diameters of the rachis: color olote: longitud mm: volumen de 100 granos: time to reach physiologic maturity: a) b) Time to flowering a) b) : a) b) Time to harvest: a) b) Yield: a) b) Planting density: Planting method: Sown system: monoculture ( ) polyculture ( ) Associated crops: Cane ( ), squash ( ), tomato ( ), cassava ( ) beans ( ), pineapple ( ) cocoa ( ), fodder ( ), axiote ( ), chili ( ), parsley ( ), others ( ) Associated vegetation 118 Problems observed during storage: control: You fertilize the corn crop: yes ( ) no ( ) How do you apply the fertilizer? Diseases observed (plant, root, stem, leaves, etc.): Disease Control: Observed insects: Insect control: Observed weeds: Weeds control: how do you plant? rainfed agriculture ( ) residual moisture ( ) irrigation ( ) What are the characteristics that you like (morphological or phenological) of the maize variety that you use? What are the characteristics that you do not like about this variety? Has your variety changed recently? What caused the change in maize variety? ( ) Did you lose the variety? ( ) The variety is no longer given ( ) other ( ) Do you want to change your variety? Why? Is the variety resistant to: flooding ( ) drought( ) pests ( ) acame ( ) Answers: resistant, susceptible, don't know Do you plant any hybrid? Which? Common name: 119 Appendix 2. In Comalcalco municipality plant species were collected in six plots with cyclical floods of 6–8 months (swamps, S) and six plots with floods of 15 continuous days (floodable areas, F) where mején and criollo maize cobs were sampled. The plants were also collected in the S and F plots and their surrounding areas in the 7 municipalities where maize cobs were sampled. Type Growth habits Family Scientific name Habitat Land Shrub C Acanthaceae Spathacanthus parviflorus Leonard F Emergent Herb Alismataceae Echinodorus subalatus (Mart. ex Schult.f.) Griseb S Emergent Herb Alismataceae Sagittaria latifolia Willd. S Tolerant Herb Amaranthaceae Amaranthus hybridus L. S, F Emergent Herb Amaryllidaceae Hymenocallis littoralis (Jacq.) Salisb. S Riparian Tree Annonaceae Annona glabra L. S Land Herb Apocynaceae Asclepias curassavica L. F Tolerant Climbing Apocynaceae Blepharodon mucronatum (Schltdl.) Decne. F Land Liane Apocynaceae Pentalinon andrieuxii (Müll.Arg.) B.F.Hansen and Wunderlin F 120 Aquatic free- floating Herb Araceae Pistia stratiotes L. S Land Herb Araceae Xanthosoma sagittifolium (L.) Schott F Land Herb Ci Araceae Colocasia esculenta (L.) Schott F Aquatic free floating Herb Araceae Lemna minor L. S Aquatic free floating Herb Araceae Lemna obscura (Austin) Daubs S Aquatic free floating Herb Araceae Lemna valdiviana Phil. S Aquatic Herb Araceae Spirodela polyrrhiza (L.) Schleid. S 121 free floating Aquatic free floating Herb Araceae Wolffiella lingulata (Hegelm.) Hegelm. S Emergent Herb Araliaceae Hydrocotyle umbellata L. S Emergent Herb Araliaceae Hydrocotyle verticillata Thunb. S Aquatic Palm Arecaceae Acoelorraphe wrightii H.Wendl. ex Becc. S Aquatic Palm Arecaceae Bactris major Jacq. var major (Bactris balanoidea (Oerst.) H. Wendl.) S Land Palm Arecaceae Sabal mexicana Mart. F Tolerant Herb Asteraceae Baltimora recta L. F Tolerant Herb Asteraceae Bidens pilosa L. F Tolerant Herb Asteraceae Eclipta alba L. ex B.D.Jacks. F Tolerant Herb Asteraceae Epaltes mexicana Less. S, F 122 Aquatic emergent Herb Asteraceae Gymnocoronis latifolia Hook. and Arn. S Land Herb Asteraceae Melampodium divaricatum (Rich. ex Rich) DC. F Land Herb Asteraceae Melanthera aspera (Jacq.) Steud. ex Small F Land Herb Asteraceae Parthenium hysterophorus L. F Tolerant Herb Asteraceae Sesbania emerus (Aubl.) Urb. S, F Land Herb Asteraceae Zexmenia serrata La Llave F Land Shrub Bignoniaceae Crescentia cujete L. F Land Tree Bignoniaceae Tabebuia rosea (Bertol.) Bertero ex A.DC. F Emergent Herb Blechnaceae Blechnum serrulatum Rich. S Emergent Herb Boraginaceae Heliotropium indicum L. S Submerged Herb Cabombaceae Cabomba aquatica Aubl. S Submerged Herb Cabombaceae Cabomba paliformis Fassett S Tolerant Herb Cannaceae Canna glauca L. F Tolerant Herb Cannaceae Canna indica L. F 123 Land Tree Capparaceae Crateva tapia L. F Land Tree Caricaceae Carica papaya L. F Land Tree Caricaceae Jacaratia mexicana A. DC. F Submerged Herb Ceratophyllaceae Ceratophyllum demersum L. S Submerged Herb Ceratophyllaceae Ceratophyllum muricatum Cham. S Land Shrub Chrysobalanaceae Chrysobalanus icaco L. F Land Herb C Cleomaceae Cleome spinosa Jacq. F Land Tree Combretaceae Terminalia buceras (L.) C.Wright F Land Herb Commelinaceae Commelina erecta L. F Land Climber I Convolvulaceae Aniseia martinicensis (Jacq.) Choisy F Land Tree Convolvulaceae Ipomoea arborescens (Humb. and Bonpl. ex Willd.) G. Don F Land Shrub Convolvulaceae Ipomoea carnea Jacq. F Tolerant Climber Convolvulaceae Ipomoea indica Merr. F Land Climber Convolvulaceae Ipomoea purpurea (L.) Roth F 124 Land Creeper Convolvulaceae Ipomoea pes-caprae (L.) R.Br. F Land Climber Cucurbitaceae Cionosicys macranthus (Pittier) C.Jeffrey Land Climber I Cucurbitaceae Momordica charantia L. F Emergent Herb Cyperaceae Cladium mariscus subsp. jamaicense (Crantz) S Emergent Herb Cyperaceae Cyperus articulatus L. S Emergent Herb Cyperaceae Cyperus canus J.Presl and C.Presl S Emergent Herb Cyperaceae Cyperus exaltatus Retz. (Cyperus odoratus L.) S Emergent Herb Cyperaceae Cyperus giganteus Vahl S Emergent Herb Cyperaceae Cyperus haspan L. F, S Emergent Herb Cyperaceae Eleocharis cellulosa Torr. S Emergent Herb Cyperaceae Eleocharis elegans (Kunth) Roem. and Schult. S Emergent Herb Cyperaceae Eleocharis mutata (L.) Roem. and Schult. var. mutata S Land Herb Cyperaceae Fimbristylis Vahl sp. F Emergent Herb Cyperaceae Fuirena camptotricha C.Wright S Emergent Herb Cyperaceae Fuirena umbellata Rottb. S 125 Emergent Herb Cyperaceae Oxycaryum cubense (Poepp. and Kunth) Palla. S Tolerant Herb Cyperaceae Rhynchospora aristata Boeckeler F, S Emergent Herb Cyperaceae Rhynchospora barbata Kunth Tolerant Herb Cyperaceae Rhynchospora colorata (L.) H. Pfeiff. F, S Emergent Herb Cyperaceae Scleria macrophylla J.Presl and C.Presl. S Tolerant Herb Euphorbiaceae Acalypha alopecuroides Jacq. F Emergent Herb Euphorbiaceae Caperonia palustris (L.) A. St.-Hil. F Land Shrub Euphorbiaceae Cnidoscolus aconitifolius (Mill.) I.M. Johnst. F Tolerant Herb Euphorbiaceae Euphorbia terracina L. F Land Herb Euphorbiaceae Euphorbia hirta L. F Land Shrub I Euphorbiaceae Ricinus communis L. F Land Shrub Fabaceae Acacia cornigera (L.) Willd. F Tolerant Herb Fabaceae Aeschynomene scabra G. Don. S Tolerant Herb Fabaceae Aeschynomene sensitiva Sw. F Land Herb Fabaceae Crotalaria incana L. F 126 Land Shrub Fabaceae Crotalaria longirostrata Hook. and Arn. F Tolerant Tree Fabaceae Dalbergia brownei (Jacq.) Urb. F, S Land Tree Fabaceae Erythrina fusca Lour. F Tolerant Tree Fabaceae Gliricidia sepium (Jacq.) Steud. F Riparian Tree Fabaceae Haematoxylum campechianum L. S Tolerant Tree Fabaceae Inga spuria Humb. and Bonpl. ex Willd. F Tolerant Tree Fabaceae Inga vera Kunth F Land Tree Fabaceae Leucaena leucocephala (Lam.) de Wit F Tolerant Tree Fabaceae Lonchocarpus guatemalensis Benth. F Tolerant Tree Fabaceae Lonchocarpus rugosus Benth. F Emergent liane Fabaceae Machaerium falciforme Rudd F Tolerant Shrub Fabaceae Mimosa pigra L. F Land Herb Fabaceae Mimosa pudica L. F Emergent Herb Fabaceae Neptunia oleracea Lour. S Tolerant Tree Fabaceae Ormosia macrocalyx Ducke F 127 Tolerant Tree Fabaceae Pithecellobium lanceolatum (Humb. and Bonpl. ex Willd.) Benth. S Tolerant Shrub Fabaceae Senna alata (L.) Roxb. F Tolerant Shrub Fabaceae Senna bicapsularis (L.) Roxb. F Tolerant Herb Fabaceae Senna occidentalis (L.) Link F Emergent Herb Fabaceae Sesbania herbacea (Mill.) McVaugh S Land Herb Fabaceae Vigna luteola (Jacq.) Benth. F Tolerant Herb Heliconiaceae Heliconia latispatha Benth. F Submerged Herb Hydrocharitaceae Najas guadalupensis (Spreng.) Magnus S Submerged Herb Hydrocharitaceae Vallisneria americana Michx. S Tolerant Herb Hydroleaceae Hydrolea spinosa L. F, S Tolerant Herb Lamiaceae Hyptis verticillata Jacq. F Free floating- submerged Herb Lentibulariaceae Utricularia foliosa L. S Free floating- Herb Lentibulariaceae Utricularia gibba L. S 128 submerged Free floating- submerged Herb Lentibulariaceae Utricularia purpurea Walter S Emergent Herb Lythraceae Ammannia coccinea Pers. S Land Liane Malpighiaceae Heteropterys laurifolia Gardner F Land Shrub I Malvaceae Abelmoschus esculentus Moench F Land Tree Malvaceae Ceiba pentandra (L.) Gaertn. F Land Tree Malvaceae Guazuma ulmifolia Lam. F Emergent Shrub Malvaceae Hibiscus striatus subsp. lambertianus (Kunth) O.J.Blanch. S, F Tolerant Tree I Malvaceae Hampea macrocarpa Lundell F Land Tree Malvaceae Hampea rovirosae Standl. F, S Tolerant Herb Malvaceae Malachra alceifolia Jacq. F Land Herb Malvaceae Malachra fasciata Jacq. F Land subshrub Malvaceae Melochia villosa (Mill.) Fawc. and Rendle F 129 Riparian Tree Malvaceae Pachira aquatica Aubl. S Land Subshrub Malvaceae Sida acuta Burm.f. F Emergent Herb Marantaceae Thalia geniculata L. S Free floating Herb Marsileaceae Marsilea ancylopoda A. Braun S Land Shrub Melastomataceae Mouriri myrtilloides subsp. parvifolia (Benth.) Morley F Floating leaves Herb Menyanthaceae Nymphoides fallax Ornduff. S Floating leaves Herb Menyanthaceaee Nymphoides indica (L.) Kuntze. S Land Tree Muntingiaceae Muntingia calabura L. S Floating leaves Herb Nymphaeaceae Nymphaea ampla (Salisb.) DC. S Tolerant Shrub Ochnaceae Ouratea nitida (Sw.) Engl. F Emergent Herb Onagraceae Ludwigia adscendens (L.) H.Hara S Emergent Herb Onagraceae Ludwigia hyssopifolia (G.Don) Exell S 130 Emergent Herb Onagraceae Ludwigia leptocarpa (Nutt.) H.Hara S Emergent Herb Onagraceae Ludwigia octovalvis (Jacq.) P.H. Raven S Emergent Herb Onagraceae Ludwigia peploides (Kunth) P.H. Raven S Emergent Herb Onagraceae Ludwigia sedioides (Humb. and Bonpl.) H.Hara S Emergent Herb Onagraceae Ludwigia torulosa (Arn.) H.Hara . S Emergent Herb Orchidaceae Habenaria Willd. S Emergent Creeper Passifloraceae Passiflora foetida L. S Tolerant Herb Passifloraceae Turnera ulmifolia L. F, S free floating Herb Phyllanthaceae Phyllanthus fluitans Benth. ex Müll. Arg. S Emergent Creeper Plantaginaceae Bacopa monnieri (L.) Wettst. S, F Tolerant Herb I Poaceae Cynodon dactylon (L.) Pers. F Tolerant Herb I Poaceae Cynodon plectostachyus (K. Schum.) Pilg. F Tolerant Herb I Poaceae Digitaria eriantha Steud. F Emergent Herb I Poaceae Echinochloa colona (L.) Link. F, S Emergent Herb I Poaceae Echinochloa crus-pavonis (Kunth) Schult. S 131 Tolerant Herb I Poaceae Eragrostis unioloides (Retz.) Nees ex Steud. F, S Emergent Herb I Poaceae Hymenachne amplexicaulis Nees S Emergent Herb Poaceae Leersia hexandra Sw. S Emergent Herb Poaceae Luziola spruceana Benth. ex Döll S, F Emergent Herb Poaceae Urochloa panicoides P.Beauv. (Panicum hirsutum Sw. ) S Emergent Herb I Poaceae Panicum maximum Jacq. S, F Emergent Herb Poaceae Paspalum fasciculatum Willd. ex Flüggé S, F Tolerant Herb I Poaceae Paspalum scrobiculatum L. F Emergent Shrub Poaceae Phragmites australis (Cav.) Steud. S Emergent Herb Poaceae Pseudechinolaena polystachya (Humb., Bonpl. and Kunth) Stap F, S Land Tree Polygonaceae Coccoloba caracasana Meisn. F Land Herb Polygonaceae Persicaria acuminata (Kunth) M. Gómez F Emergente Herb I Polygonaceae Persicaria glabra (Willd.) M.Gómez F Emergent Herb I Polygonaceae Persicaria hydropiperoides Small S, F 132 Emergent Herb Polygonaceae Persicaria punctata (Elliott) Small Free floating Herb Pontederiaceae Pontederia azurea Sw. (Eichhornia azurea (Sw.) Kunth) S Free floating Introduced Herb Pontederiaceae Pontederia crassipes Mart. S Emergent Herb Pontederiaceae Heteranthera dubia MacMill. S Emergent Herb Pontederiaceae Pontederia vaginalis Burm.f. S Emergent Herb I Pontederiaceae Pontederia hastata L. S Land Herb Portulacaceae Portulaca grandiflora Hook. F Land Herb Portulacaceae Portulaca oleracea L. F Submerged , with floating leaves Herb Potamogetonaceae Potamogeton epihydrus Raf. S 133 Submerged with floating leaves Herb Potamogetonaceae Potamogeton nodosus Poir. S Land Herb Primulaceae Bonellia macrocarpa (Cav.) B.Ståhl and Källersjö F Emergent Herb Pteridaceae Acrostichum aureum L. S Free floating Herb Pteridaceae Ceratopteris pteridoides (Hook.) Hieron. S Emergent Shrub Rubiaceae Cephalanthus tetrandrus (Roxb.) Ridsdale and Bakh.f. S Land Shrub Rubiaceae Psychotria trichotoma M. Martens and Galeotti F Land Shrub Rubiaceae Randia aculeata L. F Land Herb Rubiaceae Spermacoce ocymoides Burm.f. S Land Tree Rutaceae Zanthoxylum caribaeum Lam. F Riparian Tree Salicaceae Salix humboldtiana Willd. F, S Free floating Herb Salviniaceae Salvinia auriculata Aubl. S Free floating Herb Salviniaceae Salvinia minima Baker S 134 Free floating Herb Salviniaceae Azolla caroliniana Willd. S Free floating Herb Salviniaceae Azolla filiculoides Lam. S Mistletoe Herb Santalaceae Phoradendron carneum Urb. F Land Liane Sapindaceae Paullinia pinnata L. F Land Herb Scrophulariaceae Capraria biflora L. F Land Shrub Solanaceae Solanum donianum Walp. F Emergent Herb Solanaceae Solanum campechiense L. F, S Land Herb Solanaceae Solanum pumilum Dunal F Land Herb Solanaceae Solanum rudepannum Dunal F Land Shrub Solanaceae Solanum torvum Sw. F Emergent Herb I Sphenocleaceae Sphenoclea zeylanica Gaertn. S Emergent Creeping Thelypteridaceae Thelypteris interrupta (Willd.) K.Iwats. S Emergent Herb Typhaceae Typha domingensis Pers. S Emergent Herb Typhaceae Typha latifolia L. S Land Herb Urticaceae Urtica dioica L. S, F 135 Emergent Herb Verbenaceae Phyla lanceolata (Michx.) Greene S Emergent Herb Verbenaceae Phyla nodiflora (L.) Greene S Land Vine Vitaceae Cissus verticillata (L.) Nicolson and C.E.Jarvis F Emergent Herb Xyridaceae Xyris ambigua Beyr. ex Kunth. S Emergent Herb Xyridaceae Xyris jupicai Rich. S 136 Appendix 3. Results of the one-way ANOVA tests applied to 15 traits of the cobs of maize mején, Criollo and Hybrid in S and F plots located in 7 municipalities of Tabasco. The characteristic were: cob weight (CW), diameter at the base (DBC), center (DCC) and top of the cob (DTC), cob height (CH), number of rows cob (NR), seeds per cob (SC), seeds per row cob (SR), rachis height (RH), cob rachis weight (RW), base diameter of rachis (DBR), center diameter of rachis (DCR) and top diameter of the rachis (DTR ), relation weight cob: weight rachis (WC:WR) grain weight per cob (WG) and weight of 1000 grains (1000GW). ANOVA Table for RW _g_ by Variedad Source Sum of Squares Df Mean Square F-Ratio P-Value Between groups 9383.36 2 4691.68 105.22 0.0000 Within groups 23632.2 530 44.589 Total (Corr.) 33015.5 532 Multiple Range Tests for RW _g_ by Variedad Method: 95.0 percent Tukey HSD Variedad Count Mean Homogeneous Groups Mején 395 18.8399 X Criollo 97 21.4505 X VS-536 41 34.6488 X ANOVA Table for DBC _cm_ by Variedad Source Sum of Squares Df Mean Square F-Ratio P-Value Between groups 0.205226 2 0.102613 46.66 0.0000 Within groups 1.16548 530 0.00219903 Total (Corr.) 1.37071 532 Multiple Range Tests for DBC _cm_ by Variedad Method: 95.0 percent Tukey HSD Variedad Count Mean Homogeneous Groups Mején 395 0.412937 X Criollo 97 0.431856 X VS-536 41 0.485122 X ANOVA Table for DBR _cm_ by Variedad Source Sum of Squares Df Mean Square F-Ratio P-Value Between groups 0.187396 2 0.0936982 76.33 0.0000 Within groups 0.650603 530 0.00122755 Total (Corr.) 0.837999 532 137 Multiple Range Tests for DBR _cm_ by Variedad Method: 95.0 percent Tukey HSD Variedad Count Mean Homogeneous Groups Mején 395 0.230481 X Criollo 97 0.255258 X VS-536 41 0.296098 X ANOVA Table for DCC _cm_ by Variedad Source Sum of Squares Df Mean Square F-Ratio P-Value Between groups 0.271674 2 0.135837 87.35 0.0000 Within groups 0.824154 530 0.00155501 Total (Corr.) 1.09583 532 Multiple Range Tests for DCC _cm_ by Variedad Method: 95.0 percent Tukey HSD Variedad Count Mean Homogeneous Groups Mején 395 0.406937 X Criollo 97 0.438351 X VS-536 41 0.484878 X ANOVA Table for DCR _cm_ by Variedad Source Sum of Squares Df Mean Square F-Ratio P-Value Between groups 0.248808 2 0.124404 106.18 0.0000 Within groups 0.620959 530 0.00117162 Total (Corr.) 0.869768 532 Multiple Range Tests for DCR _cm_ by Variedad Method: 95.0 percent Tukey HSD Variedad Count Mean Homogeneous Groups Mején 395 0.213089 X Criollo 97 0.240722 X VS-536 41 0.289268 X ANOVA Table for DTC _cm_ by Variedad Source Sum of Squares Df Mean Square F-Ratio P-Value Between groups 0.114416 2 0.057207 9 18.77 0.0000 Within groups 1.61574 530 0.003048 56 Total (Corr.) 1.73015 532 Multiple Range Tests for DTC _cm_ by Variedad Method: 95.0 percent Tukey HSD Variedad Count Mean Homogeneous Groups Mején 395 0.322101 X Criollo 97 0.331134 X VS-536 41 0.377317 X ANOVA Table for DTR _cm_ by Variedad Source Sum of Squares Df Mean Square F-Ratio P-Value Between groups 3.6692 2 1.8346 36.73 0.0000 138 Within groups 26.4759 530 0.0499546 Total (Corr.) 30.1451 532 Multiple Range Tests for DTR_cm_ by Variedad Method: 95.0 percent Tukey HSD Variedad Count Mean Homogeneous Groups Mején 395 0.169646 X VS-536 41 0.214878 X Criollo 97 0.386701 X ANOVA Table for CHC _cm_ by Variedad Source Sum of Squares Df Mean Square F-Ratio P-Value Between groups 705.032 2 352.516 61.74 0.0000 Within groups 3026.07 530 5.70956 Total (Corr.) 3731.1 532 Multiple Range Tests for CHC _cm_ by Variedad Method: 95.0 percent Tukey HSD Variedad Count Mean Homogeneous Groups Mején 395 15.5891 X Criollo 97 16.568 X VS-536 41 19.8634 X ANOVA Table for RH _cm_ by Variedad Source Sum of Squares Df Mean Square F-Ratio P-Value Between groups 71.8482 2 35.9241 8.67 0.0002 Within groups 2196.81 530 4.14492 Total (Corr.) 2268.66 532 Multiple Range Tests for RH _cm_ by Variedad Method: 95.0 percent Tukey HSD Variedad Count Mean Homogeneous Groups Mején 395 16.3868 X Criollo 97 16.7999 X VS-536 41 17.7122 X ANOVA Table for NR by Variedad Source Sum of Squares Df Mean Square F-Ratio P-Value Between groups 362.323 2 181.161 60.38 0.0000 Within groups 1590.06 530 3.00011 Total (Corr.) 1952.38 532 Multiple Range Tests for NR by Variedad Method: 95.0 percent Tukey HSD Variedad Count Mean Homogeneous Groups Mején 395 11.2354 X Criollo 97 12.0309 X VS-536 41 14.2683 X 139 ANOVA Table for SC by Variedad Source Sum of Squares Df Mean Square F-Ratio P-Value Between groups 484347. 2 242173. 34.22 0.0000 Within groups 3.75117E6 530 7077.68 Total (Corr.) 4.23552E6 532 Multiple Range Tests for SC by Variedad Method: 95.0 percent Tukey HSD Variedad Count Mean Homogeneous Groups Mején 395 438.329 X Criollo 97 484.701 X VS-536 41 538.976 X ANOVA Table for WC by Variedad Source Sum of Squares Df Mean Square F-Ratio P-Value Between groups 80430.9 2 40215.5 34.65 0.0000 Within groups 615131. 530 1160.62 Total (Corr.) 695562. 532 Multiple Range Tests for WC by Variedad Method: 95.0 percent Tukey HSD Variedad Count Mean Homogeneous Groups Mején 395 141.017 X Criollo 97 157.127 X VS-536 41 184.083 X ANOVA Table for WC:WR by Variedad Source Sum of Squares Df Mean Square F-Ratio P-Value Between groups 1134.23 2 567.114 47.58 0.0000 Within groups 6316.63 530 11.9182 Total (Corr.) 7450.86 532 Multiple Range Tests for WC:WR by Variedad Method: 95.0 percent Tukey HSD Variedad Count Mean Homogeneous Groups Mején 395 13.4507 X Criollo 97 13.762 X VS-536 41 18.9683 X ANOVA Table for WG _g_ by Variedad Source Sum of Squares Df Mean Square F-Ratio P-Value Between groups 37085.8 2 18542.9 20.68 0.0000 Within groups 475235. 530 896.67 Total (Corr.) 512321. 532 Multiple Range Tests for WG _g_ by Variedad Method: 95.0 percent Tukey HSD Variedad Count Mean Homogeneous Groups Mején 395 122.177 X Criollo 97 135.676 X 140 VS-536 41 149.434 X ANOVA Table for 1000GW by Variedad Source Sum of Squares Df Mean Square F-Ratio P-Value Between groups 0.000492943 2 0.000246471 0.08 0.9214 Within groups 1.59566 530 0.00301068 Total (Corr.) 1.59615 532 Multiple Range Tests for 1000GW by Variedad Method: 95.0 percent Tukey HSD Variedad Count Mean Homogeneous Groups VS-536 41 0.278537 X Mején 395 0.280633 X Criollo 97 0.282474 X 141 Appendix 4. Productions costs of mején maize in the marceño agroecosystem in three maize productions strategies in Comalcalco municipality: traditional marceño agroecosystem (family agriculture, use the seed produced by the family, uses outside labor on a limited basis). Conventional marceño agroecosystem (include the use of some agrochemicals, buy of mején seed and external labor). Mechanized agriculture (high use of external labor, hybrid seeds and agrochemicals). Jornal = one working day (jor). Exchange rate 1 USA DLS = 19.45 pesos (March 2017). Traditional marceño family labors (Fam) Conventional marceño Mechanized agriculture I. Direct cost 1. Land preparation and sowing Concept Unit Cant. Cost Concept Unit Num ber Cost Concept Unit Number Cost Manual clearing Jor and Fam 4 $ 24.68 Manual clearing Jor 8 $ 49.36 Land clearing (mechanized) ha 1 $ 41.13 Mechanized land preparation (disc, harrow, and furrow) ha 1 $ 30.85 2. Seeds and sowing Manual planting Jor and Fam labor 4 $ 24.68 Manual planting Jor 6 $ 37.02 Planting (mechanized) ha 1 $ 30.85 Farmer´s mején maize own seeds kg 12 to 15 Mején maize seeds kg 15 $ 13.88 Maize seeds (VS-536) kg 24 $ 77.12 3. Supplies 142 Methyl parathion kg 1 $ 4.11 Herbicide (3,5,6,-trichloro- 2-pyridinyl- phosphorothioate ) L 1 $ 7.71 Systemic herbicide kg 2 $ 8.23 Fertilization (Urea Salt) kg 10 $ 5.14 Herbicide (2,4- dichlorophenoxy acetic) L 2 $ 15.42 Herbicide (2,4- dichlorophenoxyacetic) L 2 $ 15.42 Insecticide (cipermetrina) L 2 $ 18.51 First fertilization (Urea Salt) kg 50 $ 25.71 Methyl parathion kg 1 $ 4.11 Second fertilización (N 17 P17 K17) kg 12 $ 6.17 Fertilization (Urea Salt) kg 15 $ 7.71 Insecticide (cypermethrin) L 4 $ 30.85 4. Phytosanitary control Fertilization and irrigation using a backpack prayer Jor and Fam labor 1 $ 6.17 Fertilization and irrigation using a backpack prayer Jor 2 $ 12.34 Fertilization and irrigation using a backpack prayer 4 $ 20.57 1st control (Spodoptera frugiperda) Jor and Fam labor 1 $ 6.17 1st control (Spodoptera frugiperda) Jor 1 $ 6.17 First control (Spodoptera frugiperda) 2 $ 10.28 2nd control (Spodoptera frugiperda) Jor and Fam labor 1 $ 6.17 2nd control (Spodoptera frugiperda) Jor 1 $ 6.17 Second control (Spodoptera frugiperda) Jor 2 $ 12.34 1st weed control Jor and Fam labor 1 $ 6.17 1st weed control Jor 2 $ 12.34 First weed control Jor 2 $ 12.34 143 DISCUSIÓN GENERAL Importancia de los humedales en la seguridad alimentaria y los agroecosistemas tradicionales Los humedales son ecosistemas importantes que albergan una gran diversidad de especies vegetales y animales, y desempeñan un papel fundamental en la regulación del ciclo del agua y la mitigación de desastres naturales como inundaciones (Mitsch et al., 2015; Gardner y Finlayson, 2018). Existen alrededor de 1,500 a 1,600 millones de hectáreas de humedales a nivel mundial sujetos a la perdida y degradación por el cambios de uso de suelo para la expansión de las actividades agropecuarias e industriales, la urbanización, la contaminación del agua y otras actividades humanas (Convention on Wetlands, 2021; Verhoeven y Setter, 2010; Zedler, 2003). Más del 50% de la superficie de humedales, turberas, zonas ribereñas y llanuras aluviales se ha perdido, principalmente a consecuencia de la conversión a un uso agrícola intensivo, especialmente notable en América del Norte, Europa y Australia (Millennium Ecosystem Assessment, 2005). La disminución en la superficie de estos ecosistemas puede tener impactos en la calidad del agua y en la capacidad de los humedales para almacenarla y reducir inundaciones. Por lo que resulta importante promover la conservación y restauración de los humedales para proteger la biodiversidad de estos ecosistemas (Convention on Wetlands, 2018, 2021). Los humedales son vitales en la seguridad alimentaria global, su conservación y manejo sostenible son fundamentales para garantizar la disponibilidad de estos bienes naturales a futuro, por lo que es necesaria su conservación y restauración con el objetivo de proteger la biodiversidad, mitigar inundaciones y mantener una gestión sostenible de los recursos hídricos (Everard y Wood, 2018; Gardner y Finlayson, 2018). Los agroecosistemas tradicionales que han sido utilizado durante siglos en muchas regiones del mundo son ejemplos de una agricultura sostenible que permite el manejo y aprovechamiento de los humedales de manera eficiente (Koohafkan y Altieri, 2011; Mollard et al., 2008; Orozco- Segovia y Gliessman, 1979; Toledo y Barrera-Bassols, 2008). Se han realizado esfuerzos para reactivar sistemas agrícolas prehispánicos eficientes en los humedales de diferentes regiones del mundo, en el lago Titicaca con el sistema waru waru (Erickson y Candler, 1989), así como la implementación de las "chinampas chontales" en Nacajuca, Tabasco (Gómez-Pompa, 1999), que 144 replican la técnica de los sistemas chinamperos (Rojas-Rabiela, 1993). La adaptación de prácticas agrícolas tradicionales a las necesidades actuales pueden tener beneficios en términos de seguridad alimentaria y de conservación de los ecosistemas y la cultura local (Altieri, Nicholls, Henao y Lana, 2015; Denevan, 1995). Los esfuerzos a nivel local, nacional e internacional son esenciales para abordar la degradación de los humedales y promover su importancia en la sostenibilidad ambiental y el bienestar humano. Las experiencias sobre la agricultura de recesión en América, Asía y África permiten comprender la relevancia socio-ambientales y económicas que tienen estos sistemas alimentarios en regiones con población vulnerable (Balana et al, 2019; Chimweta et al., 2018; Coomes et al., 2016; Fox, 2016; Motsumi et al., 2012; Singh et al., 2021). Estos sistemas agrícolas tradicionales tienen un valor significativo desde el punto de vista cultural y ecológico que forman parte integral de la identidad de las comunidades que los practican, es decir una memoria biocultural (Toledo y Barrera-Bassols, 2008). La agricultura de recesión por inundaciones puede contribuir al manejo sostenible de los recursos hídricos al utilizar las inundaciones y avenidas de agua de manera beneficiosa para la agricultura (Balana et al., 2019; Chimweta et al., 2018; Motsumi et al., 2012; Singh et al., 2021). Verhoeven y Setter (2010) destacan la necesidad de generar investigaciones para optimizar las soluciones relacionadas con la gestión de humedales y la agricultura. Esto incluye la búsqueda de enfoques que combinen la producción de alimentos con la conservación de la biodiversidad y otros bienes o servicios ecosistémicos, así como el desarrollo y uso de cultivos más resistentes a las inundaciones como parte de un enfoque sostenible para los sistemas de llanuras aluviales. En este sentido, es necesario reforzar los estudios de los agroecosistemas tradicionales desarrollados durante milenios por los grupos culturales asentados en los humedales, como lo es el caso de los mayas chontales de Tabasco, México, los cuales han mantienen un conocimiento profundo del manejo de los ciclos hidrológicos de la planicie aluvial de Tabasco, desarrollando una cultura estrechamente relacionada con las inundaciones y los pantanos. Los agroecosistemas tradicionales en áreas de inundación, como el agroecosistema marceño, representan un conocimiento crucial para lograr la sostenibilidad y resiliencia de las comunidades rurales y los ecosistemas circundantes, como el popal que permitan preservar su patrimonio cultural y natural de Tabasco (Boege, 2008; Peraza-Villarreal et al., 2019). El agroecosistema marceño en tierras anegadas cubiertas por la vegetación hidrofito de popal, se ajustan a los ciclos de recesión de la inundación. Este sistema representa un compendio de prácticas agroecológicas 145 de manejo sostenible que permiten aprovechar, restaurar y conservar los sistemas de inundación (Gliessman, 1982; Mariaca, 1996; Orozco-Segovia y Gliessman, 1979; Orozco-Segovia y Vázquez-Yanes, 1980; Vásquez-Dávila, 2001). El pueblo maya chontal ha desarrollado una adaptación y un manejo sostenible de su entorno, especialmente en lo que respecta a las inundaciones periódicas. Esta habilidad para adaptarse a su entorno y utilizarlo ha llevado a que se les describa como una "cultura anfibia" (Vásquez-Dávila, 2001). El agroecosistema marceño representa una alternativa viable para la producción de alimentos en regiones tropicales, como Tabasco, donde el cultivo tradicional de maíz es esencial para la dieta de los agricultores de pequeña y mediana escala (Orozco-Segovia y Vázquez-Yanes, 1980; Peraza-Villarreal et al, 2019). El agroecosistema marceño se desarrolla principalmente en las localidades rurales o rancherías y territorios bioculturales mayas chontales de Tabasco. Estas áreas han sido habitadas desde la época prehispánica y tienen un relieve de terreno que varía entre 1 y 14 m s.n.m., lo que las hace propensas a inundaciones estacionales (Orozco-Segovia y Gliessman, 1979; Peraza- Villarreal et al., 2019; West et al., 1985). Actualmente este sistema agrícola se mantiene activo en 7 municipios de Tabasco, en alrededor de 203 localidades rurales, sin embargo, su práctica podría estar extendida en otras localidades con características agroecológicas similares. Como lo son las orillas del río Usumacinta en el estado de Campeche (Peraza-Villarreal et al., 2019). Varela Scherrer (2021) reporto milpas de inundación en las orillas de la laguna San Ignacio, en Palenque, Chiapas, que semejan algunas prácticas del manejo del marceño. A pesar de que la superficie en la que se practica el sistema marceño ha disminuido en el estado de Tabasco, el conocimiento tradicional relacionado a este sistema sigue siendo relevante en áreas rurales de origen maya chontal, donde el agroecosistema contribuye a la seguridad alimentaria de la población y la conservación la biodiversidad, lo que permite fortalecer la resiliencia de las comunidades frente a las amenazas ambientales, como las inundaciones estacionales (Orozco- Segovia y Vázquez-Yanes, 1980; Peraza-Villarreal et al., 2019). El modelo de distribución potencial de las comunidades vegetales asociadas al agroecosistema marceño es una herramienta importante que ayuda a identificar las áreas donde el ecosistema de popal, que ha sido perturbado por la ganadería o la desecación, es adecuado para la implementación o reconversión al sistema marceño. Lo anterior podría ser considerado y servir como una estrategia de desarrollo rural en la región de Tabasco. El análisis geoespacial realizado en esta investigación proporcionó información valiosa para la planificación y la gestión territorial 146 en la región, especialmente en lo que respecta a las áreas con inundaciones estacionales, donde la actividad ganadera y agrícola son impactadas negativamente. Es en estas áreas donde se propone la reconversión productiva e implementación del agroecosistema marceño a mayor escala. El potencial estimado para la implementación o reconversión al agroecosistema marceño constituye aproximadamente el 18.4% de la superficie estatal, es decir 4,564.11 ha. La adopción de prácticas agroecológicas que permitan la gestión sostenible de los recursos naturales y la reactivación de sistemas agrícolas tradicionales por parte de los pequeños agricultores ha sido sugerida por la FAO en la agenda 20-30 para contribuir a la mitigación de los efectos del cambio climático, con la reducción de la pobreza y la erradicación del hambre. La agricultura familiar a base del sistema marceño es fundamental para abonar a la autosuficiencia alimentaria de las comunidades de agricultores a pequeña escala de Tabasco. Las poblaciones mayas chontales de Tabasco representa el 3.6% de la población (INEGI, 2015), de los cuales el 62% habita dentro de la región biocultural “La Chontalpa, que cubre alrededor del 3.2% del área del estado, principalmente en los municipios de Nacajuca y Centla (Boege, 2008). En este territorio biocultural se ha conservado alrededor de 269.9 km2 de popal, lo que representa un importante reservorio genético de la biodiversidad de los humedales, que sin duda podría ponerse en riesgo si no se establecen políticas de manejo sostenible para su aprovechamiento. El popal es una característica distintiva de la vegetación hidrófila en las tierras bajas de Tabasco y esta abundancia se ha visto alterada debido a la falta de interés y comprensión de su relevancia cultural y ecológica. En su valor ecológico recae la conservación de la biodiversidad. Las prácticas culturales de manejo del agroecosistema marceño permiten la conservación de la flora y fauna silvestre propia de los humedales. Ya que en las parcelas de pantano e inundables, estudiadas se pudieron recolectar alrededor de 206 especies acuáticas estrictas y tolerantes a las inundaciones. Para México se han reportado 240 hidrófitas estrictas, agrupadas en 62 familias de plantas (Mora-Olivo et al., 2013). En este estudio se identificaron 103 especies acuáticas, 96 de ellas creciendo únicamente en parcelas de pantano. La diversidad de especies acuáticas respalda la relevancia de proteger los humedales de Tabasco para mantenerla y preservarla (Mora-Olivo et al., 2013). Además, estas áreas utilizadas para la agricultura marceña, proporcionan hábitat, alimento, refugio y material de anidación para una gran cantidad de especies de aves locales y migratorias (Valdez-Leal et al., 2018). Por otro lado, los popales representan el hábitat de un importante número de peces, anfibios, reptiles, crustáceos, mamíferos, invertebrados e infinidad de organismos en sus estados 147 larvarios y las plantas se utilizan como sustrato para especies epibiontes (Sánchez y Barba, 2005). El marceño desempeña un papel multifacético en la vida de las comunidades rurales y en la conservación del entorno natural. Su diversidad de productos, servicios ecosistémicos y la resiliencia que aporta son esenciales para la sostenibilidad a largo plazo de estas regiones, así como una estrategia milenaria de adaptación agrícola al ciclo hidrológico y a la dinámica de inundación de la planicie aluvial de Tabasco. El 7% del territorio maya chontal se encuentra dentro del Área Natural Protegida de la “Reserva de la Biosfera Pantanos de Centla”, una de las regiones prioritarias para la conservación de la biodiversidad. Por esa razón, nosotros proponemos solo las áreas con uso de suelo de pastizales, como áreas potenciales para la reconversión al agroecositema marceño, dada la relevancia de proteger las áreas de conservación. Los popales y el agroecosistema marceño forman parte de la identidad biocultural de las tierras bajas de Tabasco, pues la humedad residual, la fertilidad del suelo y los rendimientos significativos de maíz nativo mején (raza tuxpeño-olotillo) son aspectos positivos de este sistema agrícola, ya que aprovecha los nutrientes presentes en los suelos pantanosos de los popales, así como los que aportan las aguas residuales, lixiviados y aluviones que llegan a los pantanos con las inundaciones. Los suelos muestreados en las parcelas pantanosas e inundables se consideran adecuados para la agricultura, estos suelos no mostraron ser salinos, mantienen un pH neutro o ligeramente ácido (6.1 a 6.7), lo que favorece la disponibilidad de nutrientes esenciales para los cultivos. Por otro lado, los suelos de pantano se caracterizaron por ser extremadamente ricos en N (0.75%) y presentar niveles de P disponible de 9.65 mg kg–1, con un Ctotal de 8. 4% y una CE de 0.79 ds/cm, por lo que al ser manejados con el agroecosistema marceño brindan la oportunidad de obtener buenos rendimientos de maíz mején con un bajo uso de insumos externos. Las prácticas de manejo inherentes al agroecosistema como mantener parches de vegetación de popal dentro de las parcelas, evitar eliminar el rizoma de la planta para favorecer el rebrote, incorporar la materia orgánica del corte de la vegetación durante la práctica cultural de chaponeo, resulta vital para mantener la fertilidad de los pantanos. Por otro lado, el control temprano de la maleza es manual e inicia cuando aún la parcela está encharcada (0.3 a 0.6 m), lo que permite iniciar la descomposición de la materia orgánica (Birch, 1960; McLatchey y Reddy, 1998). Finalmente, el segundo chaponeo de la parte aérea de T. geniculata incorpora alrededor de 123 Mg ha–1 de materia orgánica fresca al suelo, lo que genera un acolchado natural que mantiene la humedad residual del suelo y controla el crecimiento temprano de arvenses durante la estación seca. 148 Asimismo, al final de ciclo agrícola se incorporan al suelo de 6.5 a 9.04 Mg ha–1 de rastrojo de maíz. Lo anterior es de gran relevancia, dado que el manejo cultural de los popales debe privilegiar la resiliencia del ecosistema después del aprovechamiento agrícola. Se ha reportado que este tipo de vegetación almacena 169.6 Mg ha–1 de carbono (COS) tanto en la planta como en los suelos, lo cual es benéfico para mantener la productividad y estabilidad de los buenos rendimientos de maíz, así como para mitigar y capturar los gases de efecto invernadero (Pellat et al., 2016). Nuestro estudio muestra que en los popales manejados con el agreoecosistema marceño el contenido relativamente bajo de C en los suelos pantanosos puede estar relacionado con el deterioro, reducción y fragmentación de los ecosistemas de popal (Díaz-Perera, 2014). Orozco-Segovia y Gliessman (1979) reportaron que la abundancia del popal disminuye con el uso del fuego usado por los agricultores para limpiar las parcelas, cazar, recolectar la fauna silvestre y el control de roedores, esta práctica da paso a la sucesión secundaria y establecimiento de Typha, Scirpus, Cyperus, Phragmites y Cladium cuyos rizomas y estolones paulatinamente sustituyen las extensa áreas de popal (Rodríguez-Arias et al., 2018). Las especies tolerantes también invaden los humedales una vez que éstos son perturbados y la invasión inicial de Poaceae y especies tolerantes ocurre desde la periferia de los cuerpos de agua hacia el centro (Rodriguez-Medina y Moreno-Casasola, 2017). A pesar de que el incendio de los popales es una práctica no generalizada relacionado con el marceño, si lo es en los pantanos conservados y perturbados (p. e. para recolecta de fauna silvestre), por lo que es necesario replantear el uso de otras estrategias de manejo de la vegetación para el aprovechamiento agrícola de los popales que permitan la resiliencia de este. Los humedales proporcionan una amplia gama de alimentos, tanto a través de la pesca de captura como de la recolección de plantas y otros organismos. Esto permite la disponibilidad de proteína de origen animal, que es esencial para la nutrición de las áreas circundantes a las zonas inundables, ya que la falta de acceso a alimentos provenientes de humedales puede llevar a la desnutrición y aumentar la susceptibilidad a enfermedades, especialmente entre las poblaciones más pobres (Everard y Woody, 2018). El agroecosistemas tradicional de áreas de humedales, como lo es el agroecosistema marceño, permite en cierta medida el abastecimiento de grano de maíz mején para el autoconsumo de 3.4 Mg ha–1 en parcelas de pantano y de 3.2 Mg ha-1 en parcelas inundables, así como la producción de hortalizas, durante la época de secas. Orozco- Segovia y Gliessman (1979), reportaron un rendimiento de grano de maíz mején y cuarentano de 149 4.5 Mg ha-1 en un popal previamente no perturbado, ubicado en Cárdenas, Tabasco, lo que sugiere que la restauración y el manejo apropiado de los popales podría incrementar el rendimiento de grano de maíz, mejorando la función de los popales en el abastecimiento de alimentos. Durante la época de inundación, la recolección y el aporte de proteína animal por medio de la cacería y recolección de la fauna silvestre asociada a los popales como quelonios, aves, peces de popal, crustáceos, mamíferos, algas, anfibios, insectos, caracoles y otros organismos contribuyen a la seguridad alimentaria de las comunidades mayas chontales de Tabasco y mestizas. Ésto es especialmente importante en áreas rurales vulnerables donde el acceso a alimentos puede ser limitado. Asimismo se recolectan materiales para la elaboración de artesanías que pueden ayudar a mantener los humedales y sus servicios ecosistémico, contribuyendo significativamente a mantener la resiliencia del ecosistema de popal y del mismo sistema marceño (Coomes et al., 2016; Mariaca, 1996; Orozco-Segovia y Vázquez-Yanes, 1980; Peraza-Villarreal et al., 2019). Además, permite diversificar las fuentes de ingresos de las familias rurales y promueve la conservación de la riqueza biocultural. Hiraoka (1985), describió las estrategias de subsistencia de una comunidad adaptada a la dinámica del río y al entorno de la llanura aluvial en la Amazonía peruana, que incluyen una combinación de agricultura, recolección, pesca y caza, que mostraban ser estrategias sostenibles y de valor significativo para el desarrollo en la región. Diversidad del maíz nativo mején El manejo cultural de variedades nativas de maíz, como el mején, puede ser importante para la conservación in situ de la diversidad genética de esta variedad, así como de los conocimientos entorno a su manejo y selección. El maíz mején, es de ciclo corto (2½ a 3½ meses) y presenta características morfológicas adaptadas a la dinámica de inundación. Las comunidades rurales de las tierras bajas de Tabasco tienen una preferencia por el maíz mején, lo que significa que lo valoran y lo cultivan de manera activa, siendo este el cultivo central del agroecosistema marceño. Esta preferencia es un factor clave en la conservación de esta variedad nativa de maíz. Entre los atributos de selección campesina del mején, resulta relevante que el sabor para la elaboración de alimentos es un rasgo importante de arraigo cultural entre los campesinos tabasqueños. Jiménez- Juárez (2012) ha demostrado que la textura de la masa mején permite que se produzca la mejor tortilla dadas sus características organolépticas en contraste con otras variedades. 150 A pesar de que el maíz híbrido VS-536 es de ciclo corto al igual que el maíz mején, la ubicación de la mazorca en la planta a una altura de 1.1-1.47 m (Zarco, 2023) no es una característica deseable en un contexto de inundación, ya que a la llegada de las inundaciones tempranas las mazorcas pueden quedar sumergidas en el agua. En el caso del maíz mején, la ubicación de la mazorca en la planta es a una altura de 1.88 m ± 0.20, lo que representa una característica importante para obtener cosechas incluso con inundación. La altura de la mazorca aumenta las posibilidades de evadir la perdida de la cosecha por la inundación, ya que para ser secada la mazorca en el campo se realiza la dobla de la planta y ésta puede ser cosechada a pesar de las inundaciones tempranas debido a que la mazorca no tiene contacto con el espejo de agua. El alto número de brácteas (totomoxtles) en la mazorca (9–13) la protegen de la alta humedad relativa, retrasa el daño causado por aves en el campo y de gorgojos durante el almacenamiento en las trojes o tapancos. Todos estos atributos hacen que los agricultores identifiquen al maíz mején como una variedad idónea para ser empleada en el agroecosistema marceño. La diversidad morfológica y la variabilidad en las características de las mazorcas del maíz mején son el resultado de la selección y el cruzamiento realizado por los agricultores a lo largo del tiempo. Esta diversidad es importante para la conservación in situ del maíz mején porque desempeña un papel crucial en la seguridad alimentaria y la cultura de las comunidades locales. La variabilidad morfológica en las mazorcas del maíz mején se atribuye al proceso de selección de semillas realizado por los agricultores. En este estudio identificamos diez atributos que han contribuido a la conservación del maíz mején: el sabor de la masa, el diámetro del raquis de la mazorca, el color del grano, la facilidad de desgrane, la ubicación de la mazorca en la planta, la precocidad, el rendimiento de grano, el número de brácteas y la tolerancia a inundaciones y sequía. En general los agricultores seleccionan semillas basadas en las características específicas que desean en sus cultivos, como el color del grano, el diámetro del raquis de la mazorca y la facilidad de desgrane de la mazorca. Para la selección de la semilla los agricultores toman la parte central de la mazorca. Al igual que en otras regiones de México la selección de la semilla se lleva a cabo principalmente en el hogar de los agricultores y es una actividad que requiere de una gran cantidad de tiempo. Se ha reportado que en algunas ocasiones los agricultores de Tlaxcala seleccionan directamente en el campo si alguna característica de la planta o de la mazorca llama su atención, aunque esta práctica se ha perdido (Llamas-Guzmán y Lazos, 2023; Magdaleno- Hernández et al., 2016). Los agricultores tabasqueños asocian un mayor número y peso del grano 151 en el maíz mején en comparación con variedades híbridas. Sin embargo, nuestros resultados solo respaldan la baja relación raquis/mazorca de 13.45 para mején y 18.96 para VS-536. El diámetro delgado del olote es una característica morfológica que los agricultores asocian con el rendimiento de grano, este es un criterio de selección al que se le da predilección durante el proceso de selección de semillas (el diámetro del olote del maíz mején es ~ 4.01 ± 0.35 cm y ~ 4.5 ± 0.3 cm en maíz VS-536). La diversidad genética del maíz mején y los conocimientos entorno al manejo del agroecosistema marceño es de gran relevancia para su conservación in situ como un reservorio genético de la agrobiodiversidad adaptada a los contextos pantanosos. Es importante continuar realizando futuras investigaciones sobre este agroecosistema y preservarlo. Finalmente, hay que señalar que es crucial mantener el uso libre de la semilla de maíz mején adaptada a los humedales de Tabasco. 152 CONCLUSIÓN  El agroecosistema marceño se practica actualmente en 203 localidades en ocho municipios de Tabasco, abarcando aproximadamente el 2% de la superficie estatal.  El 18.4% del estado de Tabasco tiene el potencial para la implementación o reconversión productiva al agroecosistema marceño.  La implementación más amplia del agroecosistema marceño podría ofrecer una alternativa para el desarrollo agrícola local, al tiempo que contribuye a la conservación y restauración ecológica de los humedales.  El agroecosistema marceño podría servir como modelo para el desarrollo agrícola en otras regiones tropicales que enfrentan inundaciones cíclicas y carecen de seguridad alimentaria.  El sistema marceño y el maíz mején representa una oportunidad para llevar a cabo estudios agroecológicos que podrían beneficiar a las comunidades en áreas de inundaciones cíclicas, que en el caso del estado de Tabasco el 61.6% de su territorio está sujeto a diferentes magnitudes de inundación cíclica. Este estudio representa la base para el desarrollo sustentable, la restauración ecológica y la conservación del paisaje biocultural de los humedales de Tabasco.  La continuidad en el futuro del agroecosistema marceño tiene un papel importante en la conservación in situ de la agrobiodiversidad porque se preserva el maíz nativo mején, el cual es un valioso reservorio genético de interés para futuras investigación y el desarrollo de nuevas variedades de ciclo corto resistentes a ambientes de alta humedad.  El agroecosistema marceño contribuye a la conservación de la flora y fauna típica de los humedales y esto es importante para la biodiversidad y el equilibrio ecológico en la región.  Este sistema también juega un papel crucial en la preservación de los conocimientos tradicionales relacionados con los humedales y el cultivo del maíz mején.  Abandonar el agroecosistema marceño representaría la pérdida de una agrobiodiversidad única en el mundo y de un paisaje biocultural que representa la identidad de las tierras bajas de Tabasco.  El agroecosistema marceño y el maíz mején se mantiene vigente en la actualidad y conserva muchas características que muestran su larga coevolución con las comunidades que coexisten con los humedales en Tabasco. 153  A pesar de su importancia histórica y sus beneficios, el agroecosistema marceño se ha reducido en superficie y se limita a unas pocas áreas y productores en la actualidad.  Los beneficios del agroecosistema marceño van más allá de los niveles locales y pueden contribuir a la seguridad alimentaria de la región.  El rendimiento del maíz mején en este agroecosistema es de 3.5 a 4 Mg ha–1 el cual se obtiene con un uso mínimo o nulo de fertilizantes inorgánicos.  La incorporación de material orgánico proveniente de la vegetación de popal y el rastrojo de cultivos aportan materia orgánica al suelo manteniendo su estructura y fertilidad.  La biomasa de rastrojo obtenidos durante el ciclo marzo-junio de 2016 para una parcela con el agroecosistema marceño fueron de 6.8 a 9.4 Mg ha–1.  El corte de popal e incorporación al suelo es una práctica tradicional que ofrece múltiples beneficios en términos de conservación de la humedad residual en el suelo, reducción del estrés hídrico y mejora de las condiciones de crecimiento de los cultivos, como el maíz mején, durante el periodo de secas. 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