Limnetica 40

Environmental filters act at different spatial scales, selecting species with characteristics that allow them to successfully establish and survive under local environmental conditions. We sought to evaluate how environmental filters (physical/chemical, habitat composition, and landscape) and different levels of anthropogenic disturbances affect the abundance of Chironomidae in neotropical semiarid watersheds. Chironomidae larvae were sampled in six reservoirs (112 sites) in the Piranhas-Assu and Paraíba watersheds (NE Brazil) during the dry season. The distribution of Chironomidae larvae was best explained in Least Disturbed sites, with 82.1 % of the total explained variance in the Piranhas-Assu watershed and 64.2 % in the Paraíba watershed. The interactions of filters (physical/chemical, habitat composition, and landscape) best explained the abundance distributions of Chironomidae larvae in the watersheds and sites subjected to different levels of anthropogenic disturbances. The physical/chemical conditions of the water as well as habitat composition depend on landscape characteristics, because anthropogenic activities in watersheds increase nutrient concentrations in the water, promoting the increase of the trophic state of the environment as well as habitat homogenization. This study showed that, independent of the anthropogenic disturbance level, interactions of environmental factors act as strong environmental filters on the distributions of local communities, such as Chironomidae assemblages.