5 CONCLUSION

A homogeneous population structure with low genetic diversity and star-like haplotype pattern was revealed for E. cardinalis in Beibu Gulf. Furthermore, pairwise comparisons of ΦST and the effective number of migrants between all sampling sites in Beibu Gulf indicated a single panmictic stock of E. cardinalis . This is mainly attributed to the free genetic exchange of E. cardinalisduring reproduction. However, E. cardinalis from the eastern South China Sea cannot disperse into Beibu Gulf because of the circulation patterns and ocean geographical features such as the semi-closed sea of Beibu Gulf. This molecular evidence revealed thatE. cardinalis from Beibu Gulf experienced colonization and population expansion during the late Pleistocene due to sea level fluctuations.