Conclusions

In the Gyirong Valley of the central Himalayas, range size of vascular plants across different life form and biogeographical affinities were found increasing uniformly along the elevational gradient, which were in accordance with the prediction of Rapoport’s rule. Climate, especially contemporary climate, was the main driver for the increasing trends of vascular plants range. Both the climate variability hypothesis and the mean climate condition hypothesis were supported in explaining the elevational variation of range size. Our results reinforce previous notion that Rapoport’s rule applies to where the influence of climate is most pronounced. Such a climate-driven variations of range size call for close attention to the impact of climate change, which has been implicated in range contractions and even extinction of many taxa.