Genetics Diversity And Population Structure Of Red Swamp Crayfish (Procambarus Clarkii) Using Microsatellite Molecular Markers

Procambarus clarkii is an alien invasive species, native to south-central USA and northeastern Mexico, this species intentionally was introduced to Nanjing China, first from Japan. Now it has widely distributed in the major river basins along the middle and lower reaches of the Yangtze River. However, little is known about the genetic diversity of the population. It is necessary to have an insight into the genetic diversity, invasion routes and population structure of red swamp crayfish population in China, so as to take some appropriate management strategies.Yangtze River, Huai River and Xin'anjiang River formed three river systems of Anhui Province. There are obvious landscape features differences between the area between the Yangtze-Huai River basins, and the area between Yangtze-Xin'anjiang River basins. Our aim was to examine how the landscape features difference influenced the dispersal movement and genetic structure of the species.We collected 182 individuals from 9 sites of three basins:Huai River, Yangtze River and Xin'anjiang River in Anhui Province. Using microsatellite markers of nine loci, we explored present genetic background of Procambarus clarkii, include population genetic diversity, genetic structure and genetic cluster pattern.In presnt study, the populations showed a high level of genetic diversity. A total of 177 alleles were detected at nine loci in nine populations. It overall expected heterozygosity and observed heterozygosity was 0.779 and 0.360 respectively. Among those populations, Wangjiang population had the highest genetic diversity, however Feixi population had the lowest one with the expected heterozygosity at 0.761 and 0.565 respectively. There was a strong heterozygote deficit, which was mainly related to overfishing.The IAM, TPM and SMM were applied to test if the microsatellites displayed a departure from the mutation-drift equilibrium, using software Bottleneck. Under the IAM, the Wilcoxon tests revealed that four populations (Cd, Ch, Dz and Wj) may have experienced a bottleneck (P<0.05). Under the TPM, the Sign tests revealed that the Cz population might have experienced a recent bottleneck (P<0.05), whereas Wilcoxon's signed rank tests showed Ch populations experienced a bottleneck (P<0.05). Under the SMM, the Sign tests revealed that three populations (Cz, Dz and Xa) might have experienced a recent bottleneck (P<0.05). AMOVA revealed that 87.04% of genetic variation could be explained by the variation within populations, whereas the remaining (12.96%) came from variation among populations.The networks constructed on 9 microsatellite loci was shown 6 mainly stocks, and showed genetic distances between the 6 genetic units using Neighbor-joining analysis. Calculation ofΔK from the structure output produced a modal value of the statistic at K= 2. Our studies also showed that there are high level of gene flows existed among different populations (Nm= 2.443), and a significant correlation was found between genetic distance and geographic distance (r= 0.33, P= 0.045), which implying that natural spread between rivers or/and lakes had the major impacts on the dispersal of crayfish. In present study, a significant jump dispersal was discovered between Xin'anjiang and Chengdonghu populations, which indicated that suggesting human-mediated dispersal play a important role in the genetic structure of Procambarus clarkii.