Importância de microhabitats na ocorrência de gêneros de ephemeroptera e trichoptera em uma ilha no rio xingu

IMPORTANCE OF MICROHABITATS IN THE OCCURRENCE OF EPHEMEROPTERA AND TRICHOPTERA SPECIES IN AN ISLAND IN RIO XINGU. This work described the abundance, richness and composition of genera and the functional food groups (GFA) of Ephemeroptera and Trichoptera (ET), in different microhabitats of a fluvial island, in Volta Grande of the Xingu River, Brazilian Amazon. Aquatic insects were collected from 30 samples located in puddles situated in the interior of the island (rocks as substrate); and another 30 samples located in the coastal margin of the island (pebble as substrate). The different facets of diversity (abundance, richness and composition of genera and GFA) were compared between puddle samples with rock substrate and those from the coastal region with pebble substrate. In total, 56 individuals were collected, distributed in 15 genera ET. The greatest estimated genera richness and the largest number of individuals occurred in the rocks of the puddle environments. The composition of genera differed between the rocks in the puddle environments and the pebbles in the coastal environments, with the community of the latter being more homogeneous. There were more scraper organisms distributed predominantly in the rocks of the puddle environments and filtering organisms arranged predominantly in the pebbles of the coastal environments. The distribution of scrapers is related to the availability of food, since the island has little vegetation and the light on the rocks is favorable for colonization by biofilm, its main food resource. In the coastal region, the greater distribution of filters is related to the greater number of fine particles suspended in water, its main food resource. The results demonstrate that even in spatially close environments, such as on a small island, differences in the availability of food resources in different microhabitats can influence the distribution in multiple facets of diversity. Thus, even in dynamic environments such as large rivers, maintaining microhabitats is important for aquatic insect communities.