Comunidades de pequenos mamíferos no Estado do Rio de Janeiro

Abstract

Many studies try to understand how communities are structured and the factors influencing this structure. It is believed that the structure of communities can be determined randomly or by specific rules. In this study we investigated the influence of environmental variables, altitude, area size and fitoecological region on the composition and richness of species, in addition to investigating the role of two rules in the structuring of communities of small mammals from Rio de Janeiro. We sampled nine communities in the Rio de Janeiro state using the same protocol and registering the species richness and the species composition of each one. The environmental variables, the altitude and the area size were reduced by Principal Component Analysis (PCA) and species composition was reduced by Multidimensional Scaling (NMDS). We used the Mantel test to verify the relationship between the beta diversity, as dependent variable, the geographical distance and the altitudinal difference, as independent variables. Through matrices of presence-absence, we analyzed the influence of the assembly rules by the generation of null models. Our results showed a relationship between the species richness and the slope land, because in areas with a greater slope there are more preserved fragments, associated with greater species richness. Communities located in the same fitoecological region show similar species composition regardless of geographical distance between them. The altitudinal differences explained the beta diversity and the communities in closest elevations demonstrated to have species compositions more similar. The ordination of the communities followed a nested pattern, not showing strong influence of competition acting as structural force. This is a pattern often found in nature and may guide decisions involving the conservation efforts. The understanding of ecological differences which are responsible for the permanence of species in fragmented landscapes can be of great importance to the development of management plans and conservation of biodiversity. In Rio de Janeiro State, investments in the conservation of more hospitable remnant areas, controlling the anthropogenic activities, seems to be a good strategy for maintaining the biological diversity.