Functional trophic groups and spatial variation of aquatic insects in a hydrographic basin of Southern Brazil

Abstract

In Brazil hydrographic basins are geographical unities used to environmental and hydric resources management, but few studies focus in the biodiversity variation within these unities. Here we present the results of spatial variation of aquatic insects in streams of a hydrographic basin in Southern Brazil. The insect composition was analyzed in relation to abundance of the families, functional trophic group and environmental evaluation indexes proposed by literature. The insects had a heterogeneous distribution in the sampling areas of the hydrographic basin. The most abundant families were Hydropsychidae, Philopotamidae and Leptophlebiidae, which demonstrate a good oxygenation of the water in the sampling streams. The most abundant functional trophic groups were gatherer-collector (20%) and scraper (18.92%). The indexes demonstrated the riverbeds of the streams are stable, with a high presence of fine particulate organic matter and they were considered heterotrophic. However, they also indicated a low abundance of shredders, which may be related to poor environmental conditions in the riparian forests. Therefore, here we found spatial variation of aquatic insects and indexes performed indicated the main human impacts as deforestation and inadequate land use. The data obtained also contributed to reinforce the importance of hydrographic basin as geographical unities for environmental conservation.