Influence of geographic predictors on beta diversity of insular snakes communities

Islands biogeography theory establishes that species richness and composition in islands result from ecological and evolutionary processes, such as immigration/emigration rate and the balance between speciation and extinction. Islands' geographic distribution, area, and distance from the mainland are important features in structuring communities of different taxonomic groups. Here, we aimed to evaluate the influence of geographic predictors on the variation of snakes' community composition. The study area encompassed 17 oceanic islands in the state of São Paulo, southeast Brazil. We recorded 40 species of snakes, with an average of 8.53 ± 8.11 species per island. We observed that islands closer to the mainland are more similar in snake composition, and more distant islands have a greater variation in composition among themselves. We verified a positive correlation between beta diversity and distance from the mainland, turnover component and distance from the mainland, nested component and distance among islands, and nestedness and island area. So, we conclude that the spatial pattern of island snake composition seems to be related to species dispersal. However, it can also be a relictual fauna pattern due to the isolation of populations due to rising sea level and the subsequent formation of the studied islands. Our results reinforces the pivotal role of geographic factors in shaping spatial patterns of insular communities.