Global Patterns and Determinants of Multiple Facets of Freshwater Fishes Beta Diversity

ABSTRACT Aim Global patterns of freshwater fish species diversity and their natural and anthropogenic determinants are relatively well documented. Yet, determinants of fish dissimilarity (beta diversity) across river basins remain poorly understood. Here, we quantify taxonomic, functional and phylogenetic beta diversity of freshwater fish across global river basins and identify the key environmental and historical drivers shaping these patterns. Location Global. Time Period 1960s–2000s. Major Taxa Studied Freshwater fish. Methods We used a global database of freshwater fishes, a trait database based on morphological descriptions and phylogenetic information calculated by phylogenetic distances. We assessed multiple facets of fish beta diversity and partitioned beta diversity into turnover and nestedness components to assess their contributions. Spearman correlation analysis was conducted to assess the relationships between them and their components. We then applied boosted regression trees (BRT) model to assess their relationships with key environmental, spatial and historical variables. Results We reported strong links between three facets of beta diversity, but species turnover contributed more strongly than nestedness to overall beta diversity, while functional and phylogenetic beta diversity exhibited contrasting patterns. We further found that geographic, climatic and historical factors all played significant roles in shaping beta diversity, with river basin area emerging as the most influential predictor. Main Conclusions Although the global patterns of the three facets of beta diversity are consistent, the contributions of turnover and nestedness are different. Our results suggest that distinguishing between turnover and nestedness dimensions of the taxonomic, functional and phylogenetic facets of biodiversity provides a comprehensive and insightful understanding of the mechanisms underlying global freshwater fish beta diversity.