Environmental factors structuring the assemblage ofaquatic insects in an epigean and hypogean stretch of aNeotropical karst stream

Abstract

The aim of the present study was to identify which variables structure the assemblage of aquatic insects in thesubterranean environment, because knowledge about how subterranean communities are structured in rivers withhypogean sections is still emerging. In addition to identifying whether the hypogean assemblage is structured in thesame way as the epigean assemblage, we sought to identify whether the environmental restrictions caused by thesubterranean habitat resulted in reduced species richness and abundance compared with the epigean habitat. We sampled a345-m stretch of a stream in Brazil and collected aquatic insects from both the epigean and hypogean environments. In thestream stretch investigated, there was a positive relationship between richness and the percentage of immersion, finesubstrate and organic matter, and a negative relationship between richness and conductivity. We also verified differencesbetween the epigean and hypogean environments regarding composition. The variables that best explained the overallassemblage structure included the epigean–hypogean environment and the percentage of coarse and fine substrate. Giventhe differences between these environments, we emphasise the need for management actions in karst regions that considerthe discontinuity of these regions’ river communities to conserve all components of diversity.