A Study On The Introgression Hybridization Among The Species Of Fushou Snail That Invaded China

Apple snails(Ampullariidae),are freshwater gastropods native to South America.They have been introduced to a number of countries of Southeast Asia,South Asia and North America.They pose seriously threat to aquatic agricultural products,ecological balance and human health in invaded areas.Pomacea canaliculata,which was listed among 100 of the world's worst invasive alien species.The invasive species of Pomacea in China are P.canaliculata,P.maculata,and P.occulta nov.sp.,a newly discovered species.The results showed that there were introgression hybridization of P.canaliculata and P.maculata in their native Argentina and other invasive countries such as Japan,Korea and Vietnam.At the same time,the analysis of EF1? sequences showed that there was genetic hybridization of P.canaliculata,P.maculata and P.occulta nov.sp.in China.This study was carried out on the invasion of China mainland area Pomacea spp.whole genome sequencing,single nucleotide polymorphism loci based on genome-wide scale,to explore the level of genetic diversity,population genetic structure and introgressive hybridization between Pomacea spp.,for further research on Pomacea spp.invasion mechanism to provide the basic data.The main results and conclusions are as follows:1.This study is based on the seven populations of 108 samples of resequencing data of P.canaliculata,P.maculata and P.occulta nov.sp.for population genetic analysis,and the results of VCFTools software analysis showed that all the three species had low genetic diversity.There were moderate and strong genetic differentiation among the six geographic populations of P.canaliculata(Fst=0.081-0.380),and the Suzhou population was the most differentiated from other populations.The data suggested that Chinese populations of P.canaliculata had multiple introductions,which may be one of the reasons for the greater differentiation among populations.There was no genetic differentiation between the two geographic populations of P.maculata.2.f3 statistical analysis based on whole-genome resequencing data showed that P.occulta nov.sp.was not a hybrid of P.canaliculata and P.maculata.And P.occulta nov.sp.and P.canaliculata from Liuzhou,Guangxi formed the same genetic cluster in the phylogenetic tree and Admixture cluster analysis,suggesting the existence of introgressive hybridization.Based on the analysis of genome-wide SNPs,it was found that there were extensive introgressive hybridization between P.canaliculata and P.maculata in Chengdu,Sichuan.Treemix gene flow analysis showed that there was gene flow between P.maculata from Chongqing and P.canaliculata,P.occulta nov.sp.from Liuzhou,Guangxi.And there was gene flow between P.maculata from Chengdu,Sichuan,and P.canaliculata from Lishui,Zhejiang.It was suggested that introgression hybridization may have occurred between the three species before or during introduction.3.In this study,based on the whole genome sequencing data of Pomacea spp.,22 SNPs were developed and verified by Sanger sequencing method.Polymorphisms of these SNPs were evaluated in 30 individuals of P.canaliculata,and most of the SNPs were found to have moderate polymorphism.Five SNPs were identified with the high Fst values and different allele frequency between P.canaliculata and P.maculata.Then these five diagnostic SNPs were genotyping by Sanger sequencing in 48 samples including P.canaliculata and P.maculata.Species identification accuracy was high and the accuracy could reach 100% when three to five diagnostic SNPs were used simultaneously.Those polymorphic SNP markers will be helpful for population genetics study on P.canaliculata and efficient and accurate species identification of P.canaliculata and P.maculata.