Factors influencing the distribution patterns of bird endemism in China

Distribution of geographically restricted and evolutionarily unique species and its underlying drivers is key to understand evolutionary patterns and conserve biodiversity. However, few studies have simultaneously tested the associations of biotic interactions, environmental heterogeneity, contemporary and paleo-climate, species traits, and human activities with patterns of bird endemism. Here, we quantified the geographic distribution patterns and drivers of species and phylogenetic endemism of 1127 bird species in China. The results showed that species and phylogenetic endemism of Chinese birds was higher in western China, especially in northwestern and southwestern China. Higher plant species richness, altitudinal range, net primary productivity, and lower temperature seasonality were associated with higher species and phylogenetic endemism. In addition, altitudinal range and net primary productivity can also indirectly influence species and phylogenetic endemism by directly affecting plant species richness. This may be because greater altitudinal range could foster more diverse habitats, and higher net primary productivity could ensure abundant food resources. Notably, species and phylogenetic endemism were also negatively associated with clutch size and cropland area. These findings identify that northwestern and southwestern China have the highest evolutionary and biogeographical uniqueness of bird assemblages, and provide insights into the evolutionary underpinnings of biogeographical patterns in Chinese birds. Meanwhile, it is crucial to conserve plant diversity, focus on groups with specific traits, and reduce human activities to better protect bird diversity.