Biodiversity under rocks in disturbed habitats: the role of microhabitats in landscape heterogeneity and community maintenance

The construction of reservoirs for electric power generation is becoming a frequent action in Brazil. In thesemodified environments, the water level suffers seasonal and stochastic oscillations. The difference among maximumand minimum water levels forms a depletion zone, in which these oscillations represent a disturbance for the installedcommunities. Analyzing 30 shelters in the depletion zone of Três Marias Reservoir, we aimed to evaluate the richnessand diversity of associated communities and verify the relationship between shelter’s area, distance from water,concentration of organic matter and humidity and communities’ traits. We collected 183 individuals distributed in 64morfo-species of 33 families from the orders Acarina, Araneida, Scorpionida, Lithobiomorpha, Scolopendromorpha,Coleoptera, Collembola, Dermaptera, Dictyoptera, Diptera, Ensifera, Homoptera, Hymenoptera, Lepidoptera, andZygentoma. Araneida was the richest order (40.4%), represented mainly by the families Salticidae and Theridiidae.Hymenoptera (18%) and Diptera (13.1%) were abundant. Nearly 68% of the species are predators, the others arebasically scavengers. Most of the species (73%) use more than a shelter for obtaining resources. The similarity amongthe shelters varied between 0 and 0.5, and most presented similarity values less than 0.3. Soil moisture was significantlyrelated to distance from water and organic matter and distance from water was also related to organic matter. Nocorrelation was observed among physical and biological variables. Shelters seem to be important in the depletionzone of the reservoir, offering conditions and resources that make the permanence of associated communities possiblein a strongly modified area subject to stochastic disturbances