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 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.

In a study published in Global Ecology and Biogeography, a team led by Prof. SU Guohuan from the Institute of Hydrobiology of the Chinese Academy of Sciences revealed that multidimensional beta diversity of freshwater fishes exhibited broadly consistent spatial patterns across the globe, although they were dominated by distinct ecological processes, advancing the understanding of mechanisms shaping freshwater fish community structure at the global scale.

By integrating global databases on species distributions, morphological traits, and phylogenetic information, researchers quantified the taxonomic, functional, and phylogenetic beta diversity of freshwater fishes at the river-basin scale, and they partitioned each dimension into turnover and nestedness components.

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, while functional and phylogenetic beta diversity were largely dominated by nestedness processes.

Through correlation analyses and boosted regression tree models, researchers comprehensively assessed the effects of geographic, climatic, and historical factors on multidimensional beta diversity and its components. They revealed that all three dimensions were jointly regulated by multiple drivers, among which basin area consistently emerged as the most influential predictor.

This study highlights 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.