Climate-induced range contraction drives genetic erosion in an alpine mammal

Increasing documentation of changes in the distribution of species provides evidence of climate change impacts, yet surprisingly little empirical work has endeavoured to quantify how such recent and rapid changes impact genetic diversity. Here we compare modern and historical specimens spanning a century to quantify the population genetic effects of a climate-driven elevational range contraction in the alpine chipmunk, Tamias alpinus, in Yosemite National Park, USA. Previous work showed that T. alpinus responded to warming in the park by retracting its lower elevational limit upslope by more than 500 m, whereas the closely related chipmunk T. speciosus remained stable. Consistent with a reduced and more fragmented range, we found a decline in overall genetic diversity and increased genetic subdivision in T. alpinus. In contrast, there were no significant genetic changes in T. speciosus over the same time period. This study demonstrates genetic erosion accompanying a climate-induced range reduction and points to decreasing size and increasing fragmentation of montane populations as a result of global warming.