Turnover is the dominant process of taxonomic and functional β-diversity on Neotropical inselbergs

The analysis of beta-diversity is a useful tool for understanding the drivers of community assembly and for quantifying the role of biodiversity in ecosystem functioning. Differentiating beta-diversity patterns into turnover and nestedness provides a better understanding of the mechanisms driving biodiversity in a community. The study of beta-diversity on inselbergs, a rare island-like habitat, can shed light on the mechanisms that cause dissimilarity patterns among communities. Previous studies of inselbergs did not differentiate between turnover and nestedness, nor did they consider functional traits. We analyzed the taxonomic and functional alpha- and beta-diversities in eight inselbergs in Southeastern Brazil. We related the decomposed components of beta-diversities to understand the contribution of turnover (beta sim) and nestedness (beta nes) to the indexes. We also tested whether functional richness follows the expected community species richness. Considering the isolated nature of the communities in each inselberg, we can presume that the dissimilarity found in these communities is primarily due to species replacement rather than nestedness assemblage. The structure and alpha-diversities showed significant differences among inselbergs and an evident oligarchic structure in plant communities. The taxonomic and functional beta-diversity were significantly correlated and their respective beta sor components. In both taxonomic and functional beta-diversities, beta sim contributed more to the beta-diversities, highlighting that not only species change between inselbergs but also functional traits. This pattern reveals that the turnover is the dominant process of taxonomic and functional beta-diversity on Brazilian Neotropical inselbergs. The findings suggest the need for conservation strategies encompassing several inselbergs within a region. These results contribute to improving our understanding of the drivers of biodiversity in plant communities and highlight the importance of considering functional traits in beta-diversity studies.