Estrutura e distribuição da fauna de Chironomidae (Diptera) em mesohabitats de um córrego de primeira ordem da Reserva Biológica Municipal Poço D'anta, Juiz De Fora (MG)

Abstract

The aim of this study was to investigate the structure and distribution of the Chironomidae fauna in mesohabitats of litter from riff1e areas, litter from pool areas, and sediment in pool areas in a first-order Atlantic Forest stream located in southeastem Brazil. The collections were carried out in the months of July, August and September of 2007 (dry season) and January, February and March of 2008 (rainy season), using a Surber sampler (250 um mesh) for a period of 30 seconds for each mesohabitat. The samples were fixed in formaldehyde solution 4%, and then washed in current water and passed through a sieve with a 0.21mm mesh, sorted in a stereoscopic microscope and identified to genus level or morphotype. ln order to analyze the structure ofthe Chironomidae community in each mesohabitat sampled in the two periods of study, the richness, the Shannon's diversity index, Pielou's evenness and the dominance index were calculated. Cluster analysis indicated that precipitation was a factor with a great influence on the variation of the structure of the Chironomidae fauna in mesohabitats from litter in riffle areas and in pool areas, with low influence on sediment in pool areas. Through the Correspondence Analysis and the lndicator Values Method it was possible to observe the association of the taxa with specific mesohabitats and/or the seasonal period. The substrates litter and sediment were suitable to the establishment of Chironomidae larvae showing high richness and diversity. The type of substrate and the precipitation were the major factors that determined the structure and spatial and temporal distribution of the fauna. The results obtained reinforce the importance of the Riparian Forest to the heterogeneity of habitats on a local scale, a fact that allows the specie diversity in low order streams.