Influence of land use on the structure and functional diversity of aquatic insects in neotropical streams

Although many studies show the negative impacts of agricultural activities on aquatic ecosystems, few relate functional and structural characteristics of the biota. We evaluate the structure and functional dynamics of aquatic insects in headwater streams with different degrees of land cover and in different hydrological periods, in a hydrographic basin where agriculture and livestock predominate. Three diversity indices were measured: functional richness (FRic), functional equitability (FEve) and functional dispersal (FDis), with the highest values recorded for Trichoptera, Diptera, Coleoptera and Odonata. From the results, the abundance was higher in the dry season and some families were exclusive to this period. In the rainy season, there was a decline in total abundance and richness of families and an increase of Diptera in urban streams. In rural streams, we registered an occurrence of Odonata, Coleoptera and EPT and a reduction of Diptera. The recorded data confirm that urbanization has negative effects on ecosystem functioning, since urban streams showed lower richness, dispersion and functional evenness. Furthermore, the increase in taxonomic diversity was accompanied by an increase in functional diversity, which reinforces the importance of the combined approach of functional and structural traits to better understand the impacts of anthropic changes in neotropical streams.