Beta diversity integrates multiple dimensions, comprising taxonomic, functional, and phylogenetic facets, each of which can be further partitioned into turnover and nestedness components. It is fundamental for characterizing compositional differences among biological communities and for inferring the underlying ecological and evolutionary processes. Although the spatial patterns of taxonomic beta diversity of freshwater fishes and its environmental and historical drivers have been extensively documented at the global scale, a systematic global assessment of the spatial patterns and formation mechanisms of functional and phylogenetic beta diversity remains elusive.

Recently, the research group led by Prof. SU Guohuan from the Institute of Hydrobiology (IHB) of the Chinese Academy of Sciences, revealed that multidimensional beta diversity of freshwater fishes exhibits broadly consistent spatial patterns across the globe, yet these patterns are dominated by distinct ecological processes. This work significantly advances the current understanding of the mechanisms shaping freshwater fish community structure at the global scale. The study has been published in Global Ecology and Biogeography.

In this study, the researchers quantified the taxonomic, functional, and phylogenetic beta diversity of freshwater fishes at the river-basin scale by integrating global databases on species distributions, morphological traits, and phylogenetic information, and further partitioned each dimension into turnover and nestedness components. The results showed that all three dimensions of beta diversity exhibited a broadly consistent global spatial pattern, characterized by a general decline from low to high latitudes. Mechanistically, taxonomic beta diversity was mainly driven by species turnover across most basins, whereas functional and phylogenetic beta diversity were largely dominated by nestedness processes.

Furthermore, through the application of correlation analyses and boosted regression tree (BRT) models, the researchers comprehensively assessed the effects of geographic, climatic, and historical factors on multidimensional beta diversity and its components. The results indicated that all three dimensions were jointly regulated by multiple drivers, among which basin area consistently emerged as the most influential predictor.

Overall, this study demonstrates that although taxonomic, functional, and phylogenetic beta diversity are highly correlated in their large-scale spatial distributions, they differ substantially in their underlying compositional processes. These findings highlight that relying on a single dimension of beta diversity is insufficient to fully capture the mechanisms shaping community differentiation. Disentangling the relative contributions of turnover and nestedness across multiple dimensions provides deeper insights into how environmental filtering, geographic isolation, and historical climate change jointly and differentially influence freshwater fish community assembly at the global scale.

Maps of freshwater fish taxonomic (TBD, TBDn and TBDt), functional (FBD, FBDn and FBDt), and phylogenetic beta diversity (PBD, PBDn and PBDt) in the global watersheds. (Image by IHB)

(Editor: MA Yun)