[Effects of environmental factors over aquatic hemimetabola and Coleoptera diversity in the Xichu's basin, Guanajuato, México]. / Efecto de los factores ambientales sobre la diversidad de insectos hemimetábolos y coleópteros acuáticos en la cuenca del Rio Xichú, Guanajuato, México.

Lotic systems, in particular temporal streams, represent an important proportion of continental waters, but are poorly studied. This is particularly clear in central Mexico, where temporal streams are abundant and remain poor studied despite their great potential for high diversity and the important energy within these ecosystems. The aim of this study was to analyze the environmental variables and scales at which these variables have effects on aquatic insect assemblages in a semiarid fluvial system in Central Mexico. A total of 89 genera were registered, the order Coleoptera showing the highest richness. Peak values for alpha diversity were found on permanent sites in the dry season (1D = 10.63), the more stable environment in permanent streams during the dry season might accounted for this pattern. Assemblages at our study sites showed low similarity (Ij < 0.45) indicating high genera replacement among sites, possibly related to differences in hydroperiod. Partition analysis indicates that variation in genera composition among rivers contributed a large proportion of the diversity (37%). Results from the canonical correspondence analysis point to mesohabitat, velocity, ecological quality, and hydrological order, as the most important variables explaining diversity patterns. In addition, hydrological condition and intermittency were important factors related to diversity (-21-22%). The results suggest that permanent sites function has species sources for intermittent sites, highlighting the need for conservation planning at the landscape level in the Xichu's basin.

Efecto de los factores ambientales sobre la diversidad de insectos hemimetábolos y coleópteros acuáticos en la cuenca del Río Xichú, Guanajuato, México / Effects of environmental factors over aquatic hemimetabola and Coleoptera diversity in the Xichu’s basin, Guanajuato, México

Lotic systems, in particular temporal streams, represent an important proportion of continental waters, but are poorly studied. This is particularly clear in central Mexico, where temporal streams are abundant and remain poor studied despite their great potential for high diversity and the important energy within these ecosystems. The aim of this study was to analyze the environmental variables and scales at which these variables have effects on aquatic insect assemblages in a semiarid fluvial system in Central Mexico. A total of 89 genera were registered, the order Coleoptera showing the highest richness. Peak values for alpha diversity were found on permanent sites in the dry season (¹D=10.63), the more stable environment in permanent streams during the dry season might accounted for this pattern. Assemblages at our study sites showed low similarity (Ij < 0.45) indicating high genera replacement among sites, possibly related to differences in hydroperiod. Partition analysis indicates that variation in genera composition among rivers contributed a large proportion of the diversity (37%). Results from the canonical correspondence analysis point to mesohabitat, velocity, ecological quality, and hydrological order, as the most important variables explaining diversity patterns. In addition, hydrological condition and intermittency were important factors related to diversity (~21-22%). The results suggest that permanent sites function has species sources for intermittent sites, highlighting the need for conservation planning at the landscape level in the Xichu’s basin. Rev. Biol. Trop. 62 (Suppl. 2): 69-80. Epub 2014 April 01.

Los sistemas lóticos integrados por cauces temporales representan una alta proporción de las aguas continentales del planeta, no obstante se encuentran entre los sistemas menos estudiados a nivel mundial. En cuanto a diversidad entomológica, el centro de México -donde se ubican estos sistemas- permanece poco estudiado a pesar del alto potencial que presenta la zona de albergar una alta diversidad y de los vínculos importantes que este grupo desempeña en los flujos de energía de los ecosistemas acuáticos. El objetivo del presente trabajo fue analizar las variables ambientales que determinan los cambios en la diversidad y las escalas en que tienen efecto, en las comunidades de insectos acuáticos de un sistema fluvial semiárido del centro de México. Se registraron un total de 89 géneros, con el orden Coleoptera presentando la mayor riqueza. Los valores más altos de diversidad alfa se encontraron sobre sitios permanentes en la temporada de sequía (¹D:10.63), lo que se atribuye a la mayor estabilidad que presentan los sistemas fluviales en esta temporada. Las comunidades establecidas sobre cauces permanentes e intermitentes presentaron baja similitud (Ij <0.45), indicando un alto recambio entre comunidades establecidas sobre cauces con diferente hidroperiodo. Los análisis de distribución (“partición”) de la diversidad indican que el mayor aporte a la diversidad regional se da por cambios en la composición de géneros a nivel de ríos (37%), entre temporadas (22%) y por el tipo de sistema (21%). De acuerdo con el Análisis de Correlación Canónica las variables de mesohábitat, velocidad de corriente, calidad ecológica y orden del cauce son las que mejor explican la variación en la presencia de los taxones. Los resultados sugieren que los sitios permanentes se encuentran actuando como fuente de especies de los sitios intermitentes y que los esfuerzos de conservación en la región deben implementarse a escala de paisaje.