Multiple β-diversity patterns and the underlying mechanisms across amphibian communities along a subtropical elevational gradient

Aim: Mountain systems offer excellent opportunities to understand beta-diversity patterns and the processes driving them. However, beta-diversity patterns and the underlying mechanisms that lead to dissimilarity in mountain amphibian communities across elevational gradients remain elusive. We aimed to evaluate how amphibian communities respond to environmental gradients with elevation and to explore how different ecological mechanisms drive elevational beta-diversity. Location: A 2600-m elevational gradient along Mount Emei in southwestern China. Methods: We investigated elevational patterns and assembly processes of pairwise beta-diversity across three dimensions (taxonomic, phylogenetic, and functional) in turnover (i.e., species replacement) and nestedness-resultant (i.e., species lose/gain) for amphibians. We compared multifaceted beta-diversity components and assessed the extent to which beta-diversity responded to environmental and elevational distances. We also quantified the standardized effect size of beta-diversity and its components using null models to examine the dynamics of niche-based and neutral processes. Results: The turnover component dominated taxonomic beta-diversity, whereas nest-edness was relatively more important for phylogenetic and functional dissimilarity. Moreover, taxonomic total dissimilarity and turnover were higher than their phylogenetic and functional analogues. Our results indicated a significant distance-decay effect for multifaceted beta-diversity of amphibians on Mount Emei and found that effects and directions of predictors on multifaceted beta-diversity were different, with temperature seasonality, annual precipitation, and elevational distance acting as the most important factors. Comparing observed patterns with null-model expectations, environmental filtering, and competitive exclusion may jointly drive elevational patterns of beta-diversity. Main conclusions: Our study emphasizes the importance of partitioning taxonomic, phylogenetic, and functional components of beta-diversity and community assembly when determining beta-diversity drivers. Although it is difficult to distinguish random communities from outcomes of niche-based processes, this work highlights the potential roles of environmental filtering and competitive exclusion in controlling elevational communities and provides insights into amphibian community assembly in a biodiversity hotspot.