Fig. 3. The distribution of genetic characteristics ofOpisopappus taihangensis and Opisopappus longilobus .
a: The distribution of Ar values; b: The distribution ofF IS values; c: The distribution ofH O values; d: The distribution ofH S values.
The F IS in this study were all negative (Table 2), with a mean F IS of -0.290 for all 17 populations, -0.081 among four groups, and -0.0174 between two species. Among these 17 populations, WML (-0.213) population had a largestF IS value, while XTSK (-0.442) had a smallestF IS value.
From the population level, obvious genetic differentiation occurred among populations (F ST > 0.15) (Table S1). At the group level, there was a significant differentiation among four groups. The F ST value was 0.31731 between OLa and OTc, 0.31418 between OLa and OTd, 0.30038 between OLb and OTc, and 0.29795 between OLb and OTd. For O. taihangensis andO. longilobus species, the F ST was 0.29418, which also showed a significant differentiation between two species.

3.2 Gene exchange /flow and migration pattern

Gene exchange results showed that the migration rates from the north groups to the south groups (0.0156-0.2958) were generally higher than that from the south groups to the north groups (0.0076-0.0151). Between OLb and OTc groups, the migration rate was lower from north to south (0.0073) than from south to north (0.0227). Within the group level, the gene migration rates within population of OLa group (0.5808) were much lower than that of the remaining three groups (above 0.95) (Fig. 4).