2.1 Population sampling
We collected a total of 210 individuals from 43 populations of P.
villosa in the field throughout its natural range in China (Table S1 &
(Figure S1) and randomly sampled five to ten individuals from each
population. We sampled individuals 20 m apart to avoid sampling a single
clone more than once. In the field, we immediately put the fresh leaves
into sealed bags filled with silica gel and then stored them in the
laboratory in a -20℃ freezer until processing. We deposited one voucher
specimen representing each population in the Herbarium of Qinghai-Tibet
Plateau Museum of Biology (QTPMB), Northwest Institute of Plateau
Biology, Chinese Academy of Sciences, China.