Climate and history explain the species richness peak at mid-elevation for Schizothorax fishes (Cypriniformes: Cyprinidae) distributed in the Tibetan Plateau and its adjacent regions

We studied elevational species richness patterns of Schizothorax fishes and identified the roles of ecological and evolutionary factors in shaping the patterns of elevational diversity. The Tibetan Plateau and its adjacent regions. We assembled distribution and altitude data for all Schizothorax species using the literature. We merged ecological and evolutionary approaches to test the relationships between species richness and ecological factors (climate, area, the mid-domain effect) or evolutionary factors (diversification rates and time of colonization). We found that species richness of Schizothorax fishes peaked at mid-elevations. Rainfall, area, the mid-domain effect and diversification rate were weak predictors of the richness pattern. Temperature showed a nonlinear relationship with species richness. Temperature and time of colonization were the most important variables in explaining the elevational diversity pattern. Our findings indicate that the time-for-speciation effect and niche conservatism play important roles in variation of species richness.