Population samples
A totally of 121 foliage samples were collected, 43 samples from five populations for C. bifida and 78 samples from nine populations for C. micholitzii , respectively (Table S1). Since there are only three C. bifida individuals in population BT, and four C. micholitzii individuals in two populations from Laos (L and W), we didn’t perform microsatellite genotyping of the above three populations as more than six individuals per population was required in microsatellite data processing. We kept the leave materials in environmentally-friendly poly (ethylene terephalate) a non-woven fabric bags and dried them with silica gel immediately. All samples were stored at -20°C until they were processed.