2.1 Study area
The study encompassed all of China’s land mass, including Taiwan and Hainan Island, but excluded the surrounding oceans and islets. Chinese mammalian fauna belongs to the Palearctic and Oriental realms, which can be further subdivided into seven biogeographic subregions (i.e., northeast China, north China, Inner Mongolia-Xinjiang region, Qinghai-Tibet region, southwest China, central China, and south China). These ecogeographic zones have high species diversity and many endemic animal species, including rodents. The present study divided the Chinese territory into a grid system of 80 × 80 km2 to eliminate the influence of spatial scale or area on species distribution patterns. Grids with less than 75% of the complete grid included in the study area were removed to prevent the incomplete grids in the coastline and boundary areas from affecting the subsequent statistical analysis. A total of 1672 grids were obtained.