Genetic divergence among the DL, YT and RC populations reached moderate levels as did that between the SS and LJ pop- ulation. Genetic variation among the remaining populations was great or extremely great. It is clear that the southern populations (SS, LJ, QG and NJD) differed from the northern (DL, YT, RC and LZ) based on FST and DC values. Given the long distance and the difference of marine ecological environment between these two regions, it was not surprising to see the divergence. The FST values between YL and other populations reached more than 0.3 and this degree of differentiation may be indicative of subspecies according to Wright (1978).
The correlation coefficient of geographic and genetic distance is not large, but it is significant, suggesting that geographic isolation can explain most of the genetic heterogeneity, although there are likely other factors that simultaneously affect genetic differentiation. Similarly, the IBD model of O. minor was also found by Lü et al. (2013).