Molecular Phylogeography Study Of Charybdis Japonica And Charybdis Bimaculata In East China Sea And Yellow Sea

Morphological variation among seven geographic populations of Charybdis japonica was studied using One way-ANOVA analysis, principal component analysis, cluster analysis and discriminant analysis. One way-ANOVA analysis revealed the difference between Charybdis japonica from different geographical populations. The cluster analysis showed that different Charybdis japonica populations generally gathering in line with the distribution of different sea areas, and there was no apparent clustering related to the geographical distance. The principal component analysis resulted in four principal components, the contributory ratios of the four principal components were 47.639%, 19.004%, 12.270% and 10.178% respectively, and the cumulative contributory ratio was 89.090%. The discriminant analysis revealed that the discriminant accuracy of Weihai and Zhoushan population were the lowest and both were 40%, the discriminant accuracy of Yangtze estuary was the highest and was 73.3%, and the average discriminant accuracy was 56.5%. The contributory ratios of two canonical discriminant functions established by discriminant analysis were 76.4% and 14.2%, respectively, and the cumulative contributory ratio was 90.7%. The discriminant analysis was almost the same with cluster analysis. This research showed that there were morphological differences between Charybdis japonica populations in East China Sea, Bohai Sea and Yellow Sea.Morphological variation among four geographic populations of Charybdis bimaculata in Jiaonan, Rizhao, Lvsi and Zhoushan was studied using One way-ANOVA analysis, principal component analysis, cluster analysis and discriminant analysis. One way-ANOVA analysis revealed the difference between Charybdis bimaculata from different geographical populations. The results of cluster analysis showed that Euclidean distance between Jiaonan population and Zhoushan population was the largest among Charybdis bimaculata populations while Rizhao population and Jiaonan population was the smallest; cluster analysis showed that there were morphological differences between East China Sea population and Yellow Sea population. The principal component analysis resulted in four principal components, the contributory ratios of the four principal components were 23.685%, 16.475%, 13.662% and 10.245% respectively, and the cumulative contributory ratio was 71.657%. Scatter diagram of the principal component indicated that the result of principal component analysis was almost the same with cluster analysis. The discriminant analysis revealed that the discriminant accuracy of Jiaonan, Rizhao, Lvsi and Zhoushan population were 73.7%, 78.6%, 36.7% and 56.7%, respectively; and the average discriminant accuracy was 61.4%. The contributory ratios of two canonical discriminant functions established by discriminant analysis were 52.7% and 35.4%, respectively, and the cumulative contributory ratio was 88.1%. The conclusion of cluster analysis and principal component analysis was supported by the result of scatter plots of canonical discriminant functions. This research showed that there were morphological differences between Charybdis bimaculata populations in East China Sea and Yellow Sea, and it seems likely to be caused by the discharge of Yangtze River, which might act as barriers restricting the dispersal of Charybdis bimaculata larvae.Some major hypotheses have been proposed to explain genetic patterns of marine species in the Northwestern Pacific Ocean, such as Pleistocene glacial cycles causing genetic differentiation and population expansion, ocean currents driving genentic homogeneity, and Yangtzer River outflow imposing a physical barrier to gene flow. Here, we examined the relative importance of such factors on population structuring of the Asian paddle crab, Charybdis japonica, in Yellow Sea, East China Sea and adjacent areas. Genetic variation in nine populations of C. japonica(n = 169), ranging from the Bohai Sea, Yellow Sea, East China Sea and the Sea of Japan, was determined from partial mitochondrial cytochrome c oxidase subunit I(COI) gene. Among the 14 haplotypes defined, a dominant haplotype H1 existed in all populations, and a relatively abundant localized haplotype H2 was found in three of the northern populations. Apparent trends in haplotype frequncy along China’s coastal waters were detected. The percentage of common haplotype H1 decreased from South to North. A weak, but significant, genetic barrier was detected in Haizhou Bay, which divided species into two groups(a northern group and a southern group). The local marine gyres and isolation by distance might be responsible for the divergence of northern and southern groups. Lack of genetic structure in the southern group and northern group populations indicates that ocean currents within groups facilitated the dispersal of C. japonica. Our study highlights the importance of local marine gyres for generating genetic structure in marine coastal species, especially those which exhibit inshore spawning in the Northwestern Pacific. The assumption that ocean current will result in broad dispersal should be carefully examined.Larval dispersal may have an important effect on genetic structure of benthic species. However, different species may choose different larval dispersal strategy. To examine the population genetic structure and larval dispersal strategy of portunid crab Charybdis bimaculata, a 658 base pair(bp) fragment of mt DNA COI gene was sequenced in this species. In total, 67 individuals were collected from five locations in Yellow Sea and East China, and 24 haplotypes were obtained. Mean haplotype diversity and nucleotide diversity for the five populations ranged from 0.2000±0.1541(Zhoushan) to 0.8333±0.1265(Nanji island), and from 0.0003±0.0005(Zhoushan) to 0.0026 ± 0.0019(Nanji island). Analysis of molecular variance and pairwise FST revealed no significant differentiation between the Yellow Sea and the East China Sea in C. bimaculata, supporting high larval dispersal ability in this species, rejecting larval retention. Mismatch distribution revealed that C. bimaculata had undergone population expansion. Larval drift in the ocean currents, and recent range expansion could be the reasons for little genetic structure in the studied area.