Diversity, pattern and ecological drivers of freshwater fish in China and adjacent areas

China is one of the megadiverse freshwater regions in the world, but the detailed diversity inventory, distribution pattern and ecological drivers are incompletely known, which hinders large-scale freshwater diversity conservation and pattern analysis at the global scale. Aiming to fill this knowledge gap, we compiled a comprehensive richness and distribution database of freshwater fishes in China and adject areas based on our long-term survey and exhaustive data collection from 165 hydrologic units at tributary and sub-basin grain. Then, we elucidated a biogeographical pattern using a β dissimilarity matrix with species presence/absence data and taxonomic relationships. Finally, we evaluated the explanatory power of three hypotheses, i.e., ‘area’, ‘energy’, and ‘history’, in explaining the diversity patterns. A total of 2,063 species utilizing freshwater habitats were identified in the study area. Among them, 1,651 freshwater species were recorded in China, of which 1034 species are endemic to China. Four major freshwater zoogeographic regions, the Palearctic, High Central Asia, East Asia, and South Asia, were identified from a dendrogram, and each region was characterized by different taxonomic categories (i.e., from species to order). ‘Historical’ factors play the most important role (43.64–62.96% of the total variation), or at least a comparable role to that of contemporary climate, in explaining the freshwater fish diversity patterns (species richness and species endemicity). In conclusion, the uplift of the Qinghai-Tibetan Plateau, nearby orogeny, and the following formation of the East Asian monsoon climate had profound impacts on the diversification and distribution of ichthyofauna in China and adjacent areas.