Population Genetic Diversity And Genetic Structure Of Zacco Platypus In Western Wuling Mountains And Adjacent Areas

Pale chub（Zacco platypus）is a common small wild fish and widely distributed in mountain streams,which belongs to family Cyprinidae in Cypriniformes.In recent years,with the rapid economic development,the resources of Z.platypus are gradually decreasing due to the destruction of aquatic ecological environment.In order to strengthen the protection and management of the germplasm resources of Z.platypus,it is urgent to assess population genetic diversity and genetic structure.Therefore,in this study,the genetic diversity and genetic structure of Z.platypus were evaluated by using microsatellite molecular markers and mt DNA Cytb to provide reference materials for the conservation and utilization of its natural resources.The main results are as follows:1.Development of microsatellite primers and population genetic of Z.platypus（1）In this study,the number of SSR containing 100 bp sequences at two ends was obtained by simplifying Restriction-site Associated DNA Sequence technology.The number of SSR that designed primers was 15226,and the primer design rate of SSR fragments was 37.12%,the four base microsatellite loci accounted for 31.11%,and 37microsatellite molecular markers were developed based on four-base microsatellite loci,and amplified in two wild populations,14 loci were successfully amplified,including 11polymorphic microsatellite loci.These microsatellite markers obtained in this study can be used as reliable markers for population genetics of Z.platypus.（2）Eleven microsatellite loci were developed to analyze the genetic diversity of seven populations in the western mountainous area of Wuling Mountain and Shennongjia forest area.The results showed that the alleles（N_A）ranged from 33（WC）to 55（XS）,with an average of 27.09.Shannon’s information index（I）of each population ranged from0.630（XS）to 0.804（JK 2）,with an average of 0.716.The observed heterozygosity（H_O）ranged from 0.182（XS）to 0.413（WC）,with an average of 0.332.The expected heterozygosity（H_E）of each population ranged from 0.343（XS）to 0.420（JK 2）,with an average of 0.364.The percentage of polymorphic loci（PPL）ranged from 72.73%（JK1）to 100%（WC）,with an average of 83.12%.Seven populations of Z.platypus had low levels of genetic diversity.The genetic differentiation index(F_ST)between the two populations ranged from 0.052（JK 1/SNJ）to 0.567（NC/SNJ）,and Nei’s unbiased genetic distance ranged from 0.041（JK 1/JK 2）to 1.665（JK 1/WC）.Three populations（XS,WC and SNJ）were detected by second-order mutation model（TPM）.The UPGMA tree and PCo A were constructed based on Nei’s unbiased genetic distance.The results showed that there were two clusters of 7 Z.platypus populations from western Wuling Mound Shennongjia forest,WC,CS,XS and NC populations were grouped as one branch,the populations of JK1 and JK2 first clustered together,and then clustered together with the SNJ population as another branch.Molecular analysis of variance（AMOVA）showed that there was significant genetic differentiation among the 7 populations(F_ST=0.459,P<0.01),there was significant genetic differentiation between the two populations（JK 1/JK 2/SNJ populations,WC/CS/XS/NC populations）(F_CT=0.206,P<0.05).And the results of cluster analysis of Structure showed that seven geographical populations of Z.platypus were divided into two optimal genetic groups.2.Population genetic analysis of Z.platypus based on mitochondrial Cytb gene sequenceUsing mitochondrial Cytb gene sequences as molecular markers,we investigated the genetic diversity,genetic structure and population history of 7 populations of Z.platypus from the western mountainous area of Wuling Mountain and Shennongjia forest area.The results showed that the mean of haplotype diversity（Hd）,nucleotide diversity（π）and nucleotide difference（K）of the population were 0.909,0.0377 and 38.496.And all mt DNA Cytb haplotypes were divided into three lineages,the populations of WC,CS,XS and NC are pedigreeⅠ,branchⅡis SNJ group and branchⅢis JK1 and JK2populations.The K2P genetic distance and F_STranged from 0.0015（JK 1/JK 2）to 0.0726（SNJ/JK 1）and 0.1200（JK 1/XS）to 0.9819（NC/JK 1）,respectively.AMOVA analysis showed that the genetic differentiation among the 7 populations was very significant（P<0.01）,and there was significant genetic differentiation among different genetic branches（P<0.05）.The mismatch distribution and neutral test showed that the seven populations of Z.platypus did not experience a colony at the overall level.