Effects of deforestation on environmental heterogeneity and its role in the distribution of fish species and functional groups in Amazonian streams

The advance of deforestation impacts freshwater ecosystems and, consequently, the environmental heterogeneity and associated biodiversity. Our objective was to examine the effect of deforestation on environmental heterogeneity (EH), species richness (SR), and functional richness (FRic) and the role of EH in the abundance of species and functional groups of stream fish. We analyzed 71 streams of the Acara-Capim basin, eastern Amazon. We used path analysis to assess whether land-use types influence the predominant vegetation cover and channel characteristics, and their indirect effect on EH, SR, and FRic. Taxa indicator threshold analysis was used to assess whether fish species and functional groups act as bioindicators of EH and percentage of forest in total catchment (PFTC). The higher percentage of secondary forest in total catchment (PSFTC) favored herbaceous understory plants and SR. The largest amount of sediments and higher PSFTC negatively influenced EH. FRic was not influenced by any of the variables. Species with high swimming ability that belong to the trophic guilds piscivores and invertivores, are associated with high values of EH and PFTC. Our results may be useful for riparian forest restoration projects, as we show which variables increase or decrease EH and demonstrate how bioindicators respond to this.