OL: Opisopappus longilobus ; OT: Opisopappus taihangensis .
The individuals growing in the same area were considered as a ”population”, and 160 samples from 17 populations were collected (Table 1). Five to ten individuals were randomly selected from each population, with at least 5m between individuals. Fresh, mature, and healthy leaves were sampled and stored in sealed bags containing silica gel, then sent back to the laboratory.
According to the geographical distribution of two species, the sampled populations were divided into four groups: the northern group ofO. longilobus (OLa: including XTDXG, BWD, JNH, QTH, SLD populations), the southern group of O. longilobus (OLb: containing XTSK, LFS, THDXG, HLT populations), the northern group ofO. taihangensis (OTc: including GLC, WML, LSZT, DSC populations) and the southern group of O. taihangensis (OTd: containing GS, BQ, JYS, FXD populations) (Fig. 1).