Multidimensional diversity patterns and community assembly of wintering waterbirds in isolated lakes within an...

Isolated lakes in subtropical floodplains serve as crucial biodiversity refuges within intensively managed agricultural landscapes. However, the ecological mechanisms underlying waterbird community assembly in these fragmented habitats remain poorly understood, limiting the development of effective conservation strategies. We conducted synchronous winter surveys (November 2022 - March 2024) across 18 isolated lakes in the Dongting Lake basin, China, and evaluated community-assembly patterns using a multidimensional diversity framework that integrated taxonomic, functional and phylogenetic perspectives. During the study period, we recorded 70 waterbird species. Species richness and abundance both increased significantly with lake area. Partitioning β-diversity revealed contrasting drivers. Turnover dominated the taxonomic and phylogenetic components, whereas functional β-diversity was driven mainly by nestedness, suggesting trait homogenisation among lakes. Null-model analyses showed that taxonomic, functional, and phylogenetic diversity did not differ significantly from stochastic expectations at the regional scale. At the local scale, functional richness (FRic) correlated positively with both functional and phylogenetic diversity. Both dimensions were also positively associated with standardized mean pairwise distances. Variance partitioning showed that pure spatial factors and shared environmental-spatial effects partially explained taxonomic β-diversity. Functional β-diversity was explained by pure environmental, pure spatial, and shared environmental-spatial factors. In contrast, only shared environmental-spatial factors accounted for variation in phylogenetic β-diversity. These findings highlight the importance of incorporating evolutionary and functional perspectives into biodiversity management. Overall, our study presents a multidimensional framework to guide effective conservation strategies and improve biodiversity outcomes in fragmented agricultural landscapes worldwide.