Assembly Processes of Waterbird Communities Across Different Types of Wetlands in the Middle Reaches of the Huaihe River Basin

Understanding the processes and potential mechanisms of species coexistence within biological communities is a key issue in biodiversity conservation. The Huaihe River Basin, situated in the transitional zone between northern and southern China, encompasses diverse wetland types in its middle reaches, including lakes, ponds, rivers, and subsidence areas. This unique combination of habitats provides an ideal natural laboratory for investigating the mechanisms governing bird community dynamics. Here, we quantified the species, taxonomic, functional, and phylogenetic diversity of waterbird communities across different wetland types. To assess patterns of species clustering or overdispersion, we compared the mean pairwise distance (MPD) and mean nearest taxon distance (MNTD) to null models, employing functional dendrograms and phylogenetic trees as analytical frameworks. Additionally, a hierarchical partitioning approach was employed to evaluate the independent contributions of multi-scale environmental variables to community assembly processes. The diversity indicators among different wetland types display asynchronous patterns, reflecting variations in ecological dynamics among these habitats, with the highest species, taxonomic, functional, and phylogenetic diversity in river wetlands. Our findings reveal that environmental filtering predominantly governs the dynamics of waterbird communities in monotonous open water bodies. In contrast, wetlands characterized by high environmental heterogeneity are primarily shaped by competitive exclusion, which emerges as a key mechanism influencing community structure. Moreover, our research demonstrates that increasing habitat diversity drives a shift in communities from functional and phylogenetic clustering to greater dispersion. Our study highlights the importance of habitat variables in structuring assemblages and suggests that increasing habitat heterogeneity will contribute to waterbird conservation.