Results Genetic diversity significantly declined with distance from centre and showed unimodal patterns along both latitude and longitude. The C-M pattern of genetic diversity along latitudinal gradient is high-latitude-skewed, with the peak at higher portion of the species’ latitudinal extent. The Sichuan Basin divided individuals into south and north clusters, whereas the Qinba Mountains did not. The general shape of the predicted distribution during the LGM is strongly similar with that of current distribution, except the Sichuan Basin.

Main conclusions Our study provides genetic evidence for the C-M hypothesis in a Cenozoic relict tree species across its distribution in China. The Sichuan Basin, rather than the Qinba Mountains, acts as dispersal barrier for a mountain tree species. Our results suggest that in situ refugia were maintained across southwest and central China during the LGM. The slight post-glacial 　northward expansion and asymmetrical south–north historical-gene flow did not result in a low-latitude-skewed C-M pattern of genetic diversity. Instead, complex topography in combination with the C-M dispersal dynamics shaped the latitudinal pattern of genetic diversity.