Population genetic analysis reveals secondary contact between Eriocheir sinensis and E. japonica in South Korea

Background The Chinese mitten crab ( Eriocheir sinensis ) and the Japanese mitten crab ( E. japonica ) of the family Varunidae, which are also critical fishery species in their native habitats, including China, Japan, and South Korea, exhibit a rare migration life history for the decapod life cycle. Eriocheir sinensis and E. japonica in South Korea may have originated from speciation or secondary contact in South Korea after speciation of these two species; however, the genetic relationship between these South Korean populations remains unclear, and need to be clarified. Objective This study examined the population genetic properties of E. sinensis and E. japonica in South Korea to reveal the origin of their co-existence. Methods Mitochondrial DNA cytochrome c oxidase I sequences of 120 E. sinensis and E. japonica from 6 sampling sites in South Korea were sequenced. Their genetic diversity and haplotype data were compared to previously reported data from the Chinese mainland, Taiwan, Japan, and Russia. Results The haplotype network, analysis of molecular variance, F ST values, Mantel test, and Bayesian skyline plot results of South Korean E. sinensis and E. japonica demonstrated that E. sinensis and E. japonica were isolated from their central populations, Chinese and Japanese populations, by the distance due to the temperature, salinity, ocean current flow, or a geohistorical event. In addition, genetic analysis indicated that the South Korean populations of the two species were marginal populations, exhibiting low genetic diversity, significant negative neutrality values, and radial haplotype networks. The current results also suggest that the Geum River is an overlapping habitat for the natural populations of E. sinensis and E. japonica in South Korea. Further research is required to examine the geohistorical and evolutionary event between E. sinensis and E. japonica in South Korea. Conclusions The co-existence of E. sinensis and E. japonica in South Korea may have originated from secondary contact after their speciation.