2.1 Sample collection
To observe as much variation of the species as possible in the wild, a total of 254 individuals belonging to three species ofNotholirion were collected based on our field explorations and past herbarium records. These individuals were from 31 populations at elevations above 2800 m in Nepal, Tibet (Xizang), Sichuan and Yunnan provinces (Figure 1 andSupplementary Table 1) . Sampling localities covered almost the entire distribution of the three species and 6 to 10 individuals were randomly sampled from each population with at least 20 m between the collected samples. Fresh leaves were collected and dried immediately with silica gel. The voucher specimens were deposited at Sichuan University Herbarium (SZ).