Spatial mismatch and congruence in the taxonomic, functional, and phylogenetic diversities of fish assemblages in China's water diversion lakes

The interplay of evolutionary, ecological, and anthropogenic processes is critical in shaping species distributions and biodiversity patterns. Recent studies highlight the importance of examining functional and phylogenetic traits to gain a more comprehensive understanding of these patterns. However, significant knowledge gaps remain regarding functional and phylogenetic diversity patterns among freshwater fish, particularly in the context of large-scale hydrological alterations such as the South-to-North Water Diversion Project (SNWDP). In this study, we investigated the spatial patterns of fish taxonomic, functional, and phylogenetic diversities and community assemblage, alongside their environmental drivers, within five impounded lakes of SNWDP. Our analysis sought to identify relationships between different aspects of diversity, assessing patterns of mismatch or congruence, and evaluating the efficacy of using one aspect as a proxy for another. Our results revealed that: 1) fish diversity and community assembly showed no longitudinal gradient, with spatial mismatches across diversity dimensions; 2) functional diversity was negatively correlated with both taxonomic and phylogenetic diversities, while the latter two showed no correlation; and 3) the SNWDP primarily affected taxonomic and functional diversities by altering water depth, nutrient status and promoting non-native species invasion, while phylogenetic diversity was mainly influenced by changes in water temperature and dissolved oxygen. These findings underscore the distinct contributions of various diversity measures and emphasize that no single measure can reliably predict another, highlighting the necessity of selecting diversity measures tailored to specific questions (e.g., for conservation or fisheries management). • SNWDP impacted fish diversity without a clear longitudinal gradient. • Functional diversity inversely correlated with taxonomic and phylogenetic. • Taxonomic and functional diversities were shaped by depth, nutrients, invasions. • Dissolved oxygen and temperature primarily affected phylogenetic diversity.