Estrutura da comunidade de insetos aquáticos em igarapés na Amazônia Central, com diferentes graus de preservação da cobertura vegetal e apresentação de chave de identificação para gêneros de larvas da ordem Odonata

Abstract

Small streams, at the Biological Dynamics of Fragmented Forest Project INPA ca. 80 Km north from the city of Manaus, were studied concerning the composition of the aquatic insects communities in different substrates. The aim of this study was to evaluate the responses of the aquatic insect community to changes on the landscape. In each one of the 21 igarapés, four samples of the principal biotopes were collected: leaf litter in riffle areas, leaf litter deposited on the bottom of the stream, sand and roots/vegetation on marginal banks. The relation between substrates and community was evaluated and we found that higher similarity values occurred between leaf litter deposited on the bottom and marginal roots/vegetation, and lower values occurred between leaf litter in riffle and sand substrates. Some collected taxa were considered indicators of one type of substrate, others showed a preference for one type of landscape. Richness was calculated using all macroinvertebrate taxa. The functional feeding groups was used to verify the structure of the community in different types of landscape. The bioindicator measures also used all macroinvertebrate taxa. In this study, changes on the landscape and on the substrate composition are important factors that induce changes in the macroinvertebrate fauna, but they do not change its trophic structure or taxonomic richness. Only drastic changes on the landscape resulted in changes of the taxa composition. The replacement of primary forest by pastures areas had the replacement of the aquatic fauna as a consequence. The aquatic insects are considered great biological indicators, but the accuracy in taxonomic identification is fundamental in the usage of this organisms in environmental integrity protocols. In this context, an identification key for ultimate ínstar larvae of Odonata is presented.