Comparison Of Systematic Geography Research Revealed That Henan Huaxi Crab And Changjiang Huaxi Creeping Hybridization

Various patterns of introgressive hybridization are observed in different animals which usually occurred in geographical adjacent species. Here, we performed a combined analysis of multilocus genetic data (mitochondrial DNA and nuclear microsatellite loci) to determine the hybridization between the endemic freshwater crabs, Sinopotamon yangtsekiense and S. honanense, with distribution adjacent and to explore the extent and the pattern of introgression presented in the natural hybridization for the true freshwater crabs. In this thesis, comparative analyses were conducted about populational genetic demography analyses, genetic diversity and phylogeographical structure of these two cogeneric species. And analyzed how these two distribution adjacent species happened the hybridization introgression. The combined mtDNA and microsatellite DNA were used to compare the phylogeographical patterns of two species, and the major conclusions are as follows:(1) Based on mitochondrial DNA (mtDNA) markers, the two species have shared haplotypes, the two species were not reciprocally monophyletic. And the Shanxian groups and Tongbai groups of S. yangtsekiense and the all of S. honanense haplotypes clustered into one clade, and frequent gene flow among three groups occurred. Two species were divided into two significant groups based on the microsatellite data, but discover some hybrids. The S. honanense and the Shanxian groups, tongbai groups occurred introgression leading the two species showed the mito-nuclear discordance And introgression between the two species presented spatial distribution characteristics.(2) Extensive mtDNA and mild nuclear gene introgression occured among the S. honanense and the Shanxian groups, Tongbai groups. The inheritance patterns, the rate of evolution, natural selection differences of the mitochondrial and nuclear genome and sex-biased dispersal may result different degree of hybridization introgression with cytonuclear.(3) Population genetic analysis (neutrality tests and Bayesian skyline plots) pointed to rapid species radiation and population expansion of the S. honanense. And the S.honanense had frequent gene flow and long-distance dispersal in the distribution area. These results suggest that was a prosperous period of the S.honanense populations. In addition, demographic analyses showed both species were impacted by the fall of temperature in last glacial maximum. We speculate that shared the glacial refugia between the S. honanense and the Shanxian groups, Tongbai groups. These phenomena played a role in promoting with two species introgressive hybridization. Parapatric distribution and shared the drainages also promote the introgressive hybridization. And the results showed that both species repeatedly happened introgressive hybridization, and this phenomenon still exists. Introgressive hybridization happened repeatedly in history and continues at present.