Interchange between flooding and drying, and spatial connectivity control the fish metacommunity structure in lakes of the Pantanal wetland

Abstract

We evaluated if the homogenizing effect of flooding and the environmental differentiation during the dry period, as reflected in fish communities, are related to the type of connection between floodplain lakes and rivers. In order to do this, we sampled fish in the early dry and the early flood hydroperiods. We estimated the fish assemblage structure, as fish species richness, abundance, biomass, and beta diversity. We found that biomass varied among connectivity levels and hydroperiods, while richness varied among hydroperiods and density was influenced by an interaction between connectivity and hydroperiod. Species composition varied as a function of both connection type and hydroperiod, but the interaction between these factors was not observed. The fish assemblage in isolated lakes differed from those in temporarily and permanently connected lakes. Beta diversity increased from the early dry to the early flood period and was higher in temporarily connected lakes than in permanently connected lakes. These results indicated that the spatio-temporal variations in local fish communities of floodplain lakes can be attributed to differences in connectivity. Consequently, they strengthen the hypothesis that dispersal plays a fundamental role in shaping the pattern of fish species diversity in floodplain lakes.