FRESHWATER FISHES BETA DIVERSITY:

PATTERNS AND PROCESSES IN THE COASTAL WATERSHEDS FROM THE ATLANTIC FOREST

Several factors promote the differentiation on patterns of distribution and in the species composition of an area. Geological time phenomena, such as changes in sea-level, might result in populational isolation, reducing the gene flow between populations, resulting in speciation events increasing the diversification of the ichthyofauna. Similarly, environmental factors have great influence in freshwater fishes’ communities. Over the last years efforts have been made seeking to increase knowledge about the freshwater fishes from the Atlantic Forest, resulting in the descriptions of species which contribute to the organization of a more complete inventory about this biome. Compiling the disperse knowledge about the presence and distribution of species resulted in the largest database exclusively with Atlantic Forest species, with information for 484 species. Besides the effort of many researches, no work was done aiming to evaluate the patterns and drivers that influence the beta diversity of these organisms in the coastal watersheds of the Atlantic Forest. Thus, the proposal of this work is to identify the drivers related to the patterns of beta diversity of the strictly freshwater ichthyofauna of the coastal basins from the Atlantic Forest. A cluster analysis was done to observe the similarity between fishes’ communities, grouping them by similarity. The total beta diversity and the contribution of turnover and nestedness were verified. Four models, consisting in groups of factors, were proposed, and analyzed using db-RDA. The beta diversity of freshwater fish of the coastal basins from the Atlantic Forest is comprised mainly by the replacement of species with tiny contribution of nestedness. The studied ichthyofauna was divided in three distinct clusters. The main drivers to influence the patterns found was from climatic factors. The influence of the orographic precipitation, caused by the presence of mountain chains close to the coast allied with high precipitation levels, was the factor that best explained the distribution patterns of the freshwater fishes of the coastal basins from the Atlantic Forest.