Evaluación preliminar de la variabilidad genética de genotipos de sésamo (sesamum indicum L.) provenientes de México.

La gran variabilidad genética del sésamo se ha demostrado por muchos estudios tanto a nivel mundial, como en Paraguay. Se trata de un rubro de importancia socioeconómica, en el que la producción nacional se enfoca principalmente en la variedad escoba blanca. A pesar de que esta variedad tiene excelente calidad de granos, presenta características indeseables para el manejo agronómico y problemas fitosanitarios. Por ende, es importante que los productores puedan acceder a variedades mejoradas. Para ello, el conocimiento de la variabilidad genética de las colecciones disponibles es de suma importancia como recurso para los trabajos de mejoramiento genético de esta especie. El objetivo de este trabajo fue evaluar de forma preliminar la variabilidad genética existente en los genotipos de sésamo provenientes de México. El experimento se llevó a cabo en el campo experimental de la Facultad de Ciencias Agrarias de la Universidad Nacional de Asunción, desde octubre de 2016 a abril de 2017. Fueron seleccionados 14 genotipos provenientes de México, pertenecientes al banco de germoplasma de la Facultad de Ciencias Agrarias. Se seleccionaron 35 caracteres morfológicos del tallo, hoja, flor, fruto y semillas del descriptor del sésamo establecido por el International Plant Genetic Resources Institute y el National Bureau of Plant Genetic Resources (2004), que fueron evaluados conforme a las indicaciones para cada carácter sugeridos por los descriptores de sésamo. Se aplicó el diseño completamente aleatorio, en el que cada tratamiento consistió en 14 genotipos con 10 repeticiones. Fue calculado el número efectivo de caracteres (Ne), medidos de acuerdo a Nei (1972, 1973) mediante el programa Popgene versión 1.32 (Yeh et al. 1997) utilizado para la estimación de los parámetros mencionados anteriormente. Se ha encontrado moderada variabilidad genética en los genotipos de sésamo evaluadosFil: Aquino Sánchez, Carlos Iván . Universidad Nacional de Asunción (Paraguay)Fil: Ayala Aguilera, Líder. Universidad Nacional de Asunción (Paraguay)Fil: Ayala Benítez, Marcela Beatriz. Universidad Nacional de Asunción (Paraguay)Fil: González Espínola, Diego Dionisio. Universidad Nacional de Asunción (Paraguay)Fil: Oviedo de Cristaldo, Rosa. Universidad Nacional de Asunción (Paraguay

Spatial non-stationarity in the distribution of fish species richness of tropical streams

Diversity gradients are observed for various groups of organisms. For fishes in streams, the water-energy, productivity, and temporal heterogeneity hypotheses can explain richness patterns. The relationship between species diversity and the variables that represent these hypotheses is generally linear and stationary, that is, the effect of each of those variables is constant throughout a geographically defined area. But the assumption of spatial stationarity has not yet been tested on a great number of diversity gradients. Therefore, we aimed to quantify the spatial stationarity in the relationships between fish species richness in small stream (653 streams) located throughout Brazil, and the water-energy, productivity, and temporal heterogeneity hypotheses using a geographically weighted regression—GWR. There was a conspicuous absence of spatial stationarity in fish species richness. Furthermore, water-energy dynamics represented a possible metabolic restriction acting on the community structuring of fish species richness in streams. This mechanism separated the fish fauna into two regions: (i) The Amazonian region, characterized by a stable climate and populations that are less resistant to climatic variation; and (ii) The central region, featured by greater ranges of temperature and fish populations that are resistant to climatic variation

A multiple hypothesis approach to explain species richness patterns in neotropical stream-dweller fish communities.

Several hypotheses are used to explain species richness patterns. Some of them (e.g. species-area, species-energy, environment-energy, water-energy, terrestrial primary productivity, environmental spatial heterogeneity, and climatic heterogeneity) are known to explain species richness patterns of terrestrial organisms, especially when they are combined. For aquatic organisms, however, it is unclear if these hypotheses can be useful to explain for these purposes. Therefore, we used a selection model approach to assess the predictive capacity of such hypotheses, and to determine which of them (combined or not) would be the most appropriate to explain the fish species distribution in small Brazilian streams. We perform the Akaike's information criteria for models selections and the eigenvector analysis to control the special autocorrelation. The spatial structure was equal to 0.453, Moran's I, and require 11 spatial filters. All models were significant and had adjustments ranging from 0.370 to 0.416 with strong spatial component (ranging from 0.226 to 0.369) and low adjustments for environmental data (ranging from 0.001 to 0.119) We obtained two groups of hypothesis are able to explain the richness pattern (1) water-energy, temporal productivity-heterogeneity (AIC = 4498.800) and (2) water-energy, temporal productivity-heterogeneity and area (AIC = 4500.400). We conclude that the fish richness patterns in small Brazilian streams are better explained by a combination of Water-Energy + Productivity + Temporal Heterogeneity hypotheses and not by just one