Limnetica 38

This study analyzed the functional organization of Siluriformes assemblages during one hydrological cycle in the floodplain of the Arauca River, in Venezuela, in relation to species morphologies. The study encompassed the stream La Piedra and the floodplain lake Arenosa. The functional organization of the assemblages was studied through the analysis of the Siluriformes species distributions within the morpho-space and the relation between morphological divergences and the coexistence patterns between species. The Siluriformes were more closely positioned than randomly expected within the morpho-space in the stream during August 2014 and in the lake during August 2015, whereas the morpho-space was smaller than expected in the lake during May 2015. Likewise, morphologically close species segregated spatially within the stream during July 2014, whereas they aggregated in the lake during August 2014. Altogether, these results suggest that the assembly of Siluriformes in the Arauca floodplain, as well as the strength of biotic and abiotic factors on the organization processes, can vary as a result of seasonal fluctuations in the water level and as a function of the habitat type.