Local species turnover increases regional bird diversity in mangroves

Understanding patterns of species diversity and distribution is crucial for the development of adequate public conservation policies. Despite the conservation value of mangroves, we still have a limited understanding of the influence of the habitat characteristics and patch connectivity of mangroves on bird species composition and diversity at local and regional scales. Here we used 40 point counts in six mangroves in southern Brazil to test the effects of landscape connectivity and habitat characteristics on the composition and diversity of mangrove bird communities. We measured environment variables locally and calculated land cover to describe the landscapes in which the patches of mangrove habitat were inserted. We also generated spatial variables as proxies for connectivity. We found that local bird species richness was similar in the different mangroves, ranging from 22 to 33 species, but with more species being found in larger patches. The partitioning of the beta diversity revealed a high species turnover, indicating that each patch of mangrove contributes different species to the regional pool of 57 species. Variance partitioning analysis also indicated that the composition of the mangrove bird metacommunity is driven mainly by local patch dynamics, whereas habitat characteristics and connectivity had a minor influence. These findings indicate that the maintenance of multiple large patches of mangrove at a regional scale will ensure a high species turnover and is the key to the maintenance of a diverse regional biota.