Benthic cover and community structure on shallow marine habitats in a transitional ecotone in Brazilian coast

Understanding species distribution and biodiversity patterns is an old challenge in ecology and biogeography. Nowadays, this approach is especially important due to current increase of anthropogenic pressure on coastal ecosystems. Brazilian coastline is a mosaic of complex marine habitats, including extensive rocky shores on south-southeast and the largest coral reef formation of Atlantic in southeast-northeast. Here, we investigated how benthic community are structured and species composition changes along transitional zone between rocky and coral reefs. Assessing spatial components of alpha diversity, we also analyze how species richness varies between neighboring habitats. By decomposing beta diversity into nestedness and turnover components we investigate similarities between communities and understand how beta diversity varies along this area. Our findings show differences between southern communities, associated with suspension feeders and northern communities dominated by stony corals, in a north-south diversity gradient. Redundancy Analysis indicates that temperature was the most important environmental factor shaping communities. Pairwise comparison of beta diversity shows highest turnover rates between southern and northern communities, suggesting differentiation between two bioprovinces. Based on these analyses, we recognize different patterns of diversity among communities and detect different levels of vulnerability should a stochastic event occur. Considering that human interference tends to become more intense and frequent in this area, use of beta diversity partition can be a useful analytical tool to recognize communities with different levels of priorities for monitoring and establishing conservation efforts.