Patterns and drivers of waterbird alpha and beta diversity are different between arid and humid regions of China

Waterbirds are vital for wetland ecosystems, but climate change and human activities are harming these habitats globally, reducing biodiversity and threatening waterbird survival. In China, wetlands in humid and arid regions face quite different threats, necessitating targeted conservation strategies. However, few studies have assessed the relative roles of various drivers in determining geographical patterns of alpha and beta diversity of wetland waterbirds in different regions, particularly from the perspectives of taxonomic, phylogenetic and functional diversity. This study aims to connect climate and landscape variables with waterbirds diversity in 71 wetlands across China's humid and arid regions. The results showed that mean annual temperature was negatively associated with taxonomic diversity but positively correlated with phylogenetic structure. Phylogenetic and functional diversity was significantly associated with paleoclimate change. Additionally, patch richness was positively correlated with taxonomic diversity and functional structure, but negatively correlated with phylogenetic diversity and structure. Notably, taxonomic and phylogenetic beta diversity was dominated by turnover, while functional beta diversity was dominated by nestedness-resultant components. Total edge and patch density were significantly correlated with waterbird beta diversity. In addition, arid regions showed higher turnover in taxonomic and phylogenetic diversity compared to humid regions. Compared to arid regions, humid regions had consistently higher nestedness-resultant components in the three diversity dimensions and higher turnover in functional beta diversity. These findings indicated that while climate variables are important for waterbird diversity patterns, wetland's landscape characteristics could also play significant roles. In addition, conservation of Chinese wetland bird diversity should consider unique strategies for different biodiversity dimensions as well as for different regions.