Genetic Variation And Adaptive Evolution In The Mitten Crab

The Chinese mitten crab (Eriocheir sinensis), the Japanese mitten crab (Eriocheir japonica) and the Hepu mitten crab (Eriocheir hepuensis) are important economical species in the mitten crab which have wide distribution in the East Asian. The Chinese mitten crab has been introduced to Europe and North America. In this study, we used microsatellite locus to detect the Genetic variation and adaptive evolution in the Chinese mitten crab,Hepu mitten crab and Japanese mitten crab.1,Microsatellite markers development in the Hepu mitten crab and Japanese mitten crabThe Hepu mitten crab (Eriocheir hepuensis) is an endangered freshwater crab found in the southern part of China. In this study, 15 polymorphic microsatellite loci were isolated and population genetic parameters were evaluated in three populations of E. hepuensis sampled in 1998 and 2008. The average number of alleles per locus ranged from 6.3 to 8.4, while the average observed (HO) and expected (HE) heterozygosities were from 0.725 to 0.817 and from 0.756 to 0.780, respectively. The average polymorphism information content (PIC) ranged from 0.699 to 0.756. Significant genetic differentiation was observed for E. hepuensis in the current decade (from 1998 to 2008). This suite of microsatellite loci will facilitate future studies on population structure and genetic introgression of the endangered E. hepuensis.The Japanese mitten crab (Eriocheir japonica) is a catadromous species endemic to East Asia with the widest distribution of all species in the mitten crab taxonomy. To date, no novel microsatellite loci for this species have been reported. Twenty polymorphic microsatellite loci were isolated, and cross-amplification was conducted in the Yangtze and Yellow River populations of Chinese mitten crab (Eriocheir sinensis). Four loci were found to deviate significantly from the Hardy-Weinberg equilibrium. Similar numbers of alleles, mean observed (HO) and expected (HE) heterozygosities, mean gene diversity, and inbreeding coefficients (FIS) were detected in the two populations of E. sinensis. We concluded that this suite of microsatellite loci was successful for cross-amplification in E. sinensis and might be useful for the assessment of population structure of the mitten crab.2,Genetic variation and adaptive evolution between the native and invasive Chinese mitten crabThe Chinese mitten crab (Eriocheir sinensis), a native species in China, has been introduced to Europe and North America and has posed great influences on invaded ecosystems because of its rapid expansion. In this study, genetic variation and diversity of the Chinese mitten crab between its native habitats (The Yangtze and Yellow Rivers in China) and the invade rivers (the Elbe River in Germany, Rhine River in Netherlands, Thames River in UK and the San Francisco Bay in USA) were investigated using twenty microsatellites loci. The results found the native populations possess higher genetic diversity than the introduced populations, and significant genetic differentiation between the native and invasive populations, and among the invasive populations. Bayesian clustering analysis showed significant genetic cluster of the invasive population from the native rages, and also significant genetic variation between the North American and European populations. Principal component analysis (PCA) indicated the high level of genetic differentiation in invasive populations from the native populations. However, only the Rhine River was detected significant bottleneck sign. A number of private alleles observed in the invasive populations suggested adaptive evolution occurred in colonized process.3,Genetic variation and introgression between the Chinese mitten crab and the Hepu mitten crabThe Chinese mitten crab and the Hepu mitten crab have the different distribution areas, the Chinese mitten crab mainly distributes in the northern part of the Changjiang river (including in Changjiang river), and the Hepu mitten crab distributes in the Zhujiang and Nanliujiang Rivers, while the Oujiang and Minjiang are the dilution zone of the Chinese mitten crab and Hepu mitten crab. In this study, genetic variation and introgression between the Chinese mitten crab and the Hepu mitten crab (Zhujiang) were investigated using six microsatellites loci. The results found the Chinese mitten crab in the Yangtze River had the highest polymorphism information content, while the Hepu mitten crab (ZJ) were the lowest; there were significant genetic differentiation between the pair population comparison with the exception of the Yellow (YR) and Liaohe (LH) Rivers (P=0.351). There was a closest genetic distance between the YR and LH(2.856) based on the NJ tree; Bayesian genetic alignment results indicated that the OJ population and MJ population may have crossed and made genetic introgression between them.