Spatiotemporal diversification of the largest Chinese freshwater crab genus <i>Sinopotamon s.l.</i> (Potamidae) facilitated by the East Asian summer monsoon

Abstract Palaeoclimate and palaeogeological events are crucial factors influencing the diversity and distribution patterns of organisms. However, the effects of these two factors in driving species diversification have rarely been explored in freshwater zoobenthic fauna. Here, we use the widespread East Asian freshwater crab genus Sinopotamon s.l. to investigate how its diversification has been shaped over time by the East Asian monsoon and by the reorganization of its river drainages. We used multi-locus genetic and morphological data for 79% of the species of Sinopotamon s.l. to analyse the phylogeny, biogeographical history, and diversification dynamics of the genus. Our total-evidence phylogeny strongly supports the polyphyly of Sinopotamon s.l. The reorganization of the Yangtze River drainage after the Miocene mediated the downstream range expansion of these crabs. In addition, our findings suggest that the diversity of Sinopotamon s.l. increased rapidly in the late Miocene and that the diversification dynamics of the most species-rich clade were positively associated with precipitation- and temperature-dependent speciation models. We speculate that the intensification of the East Asian summer monsoon during the late Miocene provided new ecological opportunities that promoted crab diversification. Our study highlights the importance of past climate changes in driving the rapid diversification of freshwater zoobenthic fauna.