Distribuição espacial e diversidade da comunidade zooplanctônica em áreas úmidas no sul do Brasil

Abstract

The distribution of species among sites can be influenced by processes related to biotic and abiotic factors (species sorting) and by processes independent of the environment (spatial processes). Zooplankton is strongly influenced by species sorting processes, although the importance of each process depends on geographic distance, landscape configuration, dispersal hability and life cycle phases of species. In temporary ponds zooplankton responds rapidly to changes in the environment and can be found in both the water column (active phase) and the sediment (dormant phase). The spatial distribution and effects of environmental gradients on the structure of active and dormant phase zooplankton remain unknown. In this sense, the general objective of this thesis was to evaluate the distribution of zooplankton at different spatial scales and to verify the influence of geographic distance and environmental predictors (local and regional) associated to variation of beta diversity, and additionally, to test concordance on the structure of active and dormant phases of zooplankton along a transition region between the Forest and Grassland biomes in southern Brazil. The study was carried out in twelve intermittent ponds along a forest-grassland transition in southern Brazil, within a 520-km. A total of 124 zooplankton taxa were found. The main results were that the zooplankton dormant phase was structured by local environmental factors (physical and chemical variables and habitat structure) and the active phase was structured by local (habitat structure) and regional factors (climate). Concordance patterns in species richness and composition were not found between phases and the evaluation of the active phase resulted in greater species richness. The beta diversity of the dormant phase showed greater variation in the scale of ponds, mainly in the Atlantic Forest biome. In relation to the groups, Rotifera was structured by local environmental factors and Cladocera and Copepoda were structured by both (local and regional). Concordance patterns significative were found between the richness of Cladocera and Rotifera (dormant phase), and between Cladocera and Copepoda (active phase). Significative concordance was also found in the composition of Cladocera and Copepoda and Rotifera and Copepoda. The combined results of both phases indicate that species sorting process explained the structure of zooplankton metacommunities, although the phases were distinctly affected by local and regional environmental predictors. The lack of concordance on richness and composition between phases indicates that the dormant phase are not adequate surrogates of active phase in temporary ponds, under similar incubation conditions. However, there is initial evidence that cladocerans and copepods can be employed as surrogates of other groups in temporary ponds, if the conclusions are strictly limited to similar life phase. In addition, as both respond to climate, expected that Cladocera and Copepoda may be more affected by climate change predicted for decades to come. These results may be useful for the planning of restoration and conservation strategies for temporary ponds of transition areas between grassland and forested biomes, since different environmental variables and spatial scales influenced zooplankton composition in the region.