Analysis Of Population Genetics Of Unio Douglasiae From Main Lake Located In The Middle And Lower Reaches Of Yangtze River Based On Microsatellite DNA And Mitochondrial DNA

This study represents the first analyses of population genetics and population historical dynamics o f Unio douglasiae from important lake located in the middle and lower reaches of Yangtze River based on microsatellite DNA and mitochondrial DNA.Microsatellite DNA The microsatellite DNA results showed that 434 alleles were detected among the seven sampling sites.The number of alleles(NA)at each sampling location ranged from 3.231 to 5.692,the effective number of alleles(NE)ranged from 2.223 to 2.538,observed heterozygocity(Ho)ranged from 0.454 to 0.522,expected heterozygosity(HE)ranged from 0.442 to 0.531,and PIC ranged from 0.435 to 0.477.Wilcoxon test showed some evidence for a recent genetic bottleneck at all of the locations except for LZ population using the SMM model.Except for GJ population,IAM,TPM,and mode-shift tests did not indicate the presence of a recent bottleneck at all of locations.Further analysis when all sampling locations were combined into a single population produced a similar result,with a significant indication of a recent bottleneck occurring only when assuming the TPM and SMM model of evolution.The AMOVA results showed that 36.0% of the total genetic variance was among the seven collection locations,and among sampling location differentiation was significant.Pairwise Fst and Nm among the seven collection loc ations showed that genetic differentiation was significant and that gene flow was high between DT,PY and GJ populations.Using the data generated from the STRUCTURE analys is,the Evanno et al.(2005)?K method indicated that the most likely number of populations was five.Sites DT,PY and GJ formed one genetic population,HZ,TH and LZ formed second genetic population and most specimens collected from site XN formed an independent genetic population.Genetic differentiation as represented by pairwise genetic distance values between all seven sample sites were shown to be not correlated with geographic water distance indicating that more geographically distant site combinatio ns did not produce higher levels of genetic differentiation.Moreover,a significant correlation was detected,the analysis produced a low.The ? mode values were very near.The highest ? values were found in DT,and the lowest ? values belonged to XN.The most gene flow occurred among the neighbor populations,while substantial long-distance gene flow also existed in some population pairwise.In general,the greater populations had higher gene flow.In the study,the gene flow among populations was asymmetric in both dataset.DT,HZ and GJ was a mainly source of genetic migrants into the other populations,but comparatively little gene flow occurred in the opposite direction.Mitochondrial DNAWe found 37 unique COI haplotypes in the 7 populations based on mitochondrial DNA.The GJ population had the greatest variation with 13 haplotypes,and the lowest was PY,4 haplotypes.Haplotypes diversity va lues at each population were greater,ranging from 0.857-0.975.Nucleotide diversity values ranged from 0.00726-0.04592.At the 95% confidence limit,Network software produced a single network.From all the U.douglasiae sequences analysed,37 distinct hap lotypes were resolved,64 of which occurred only once with the most frequent haplotype(H16)occurring in 6 individuals,and 23 haplotypes were rare haplotype(only 1 individual).H29 and H17 was unique haplotype from XN and PY,respectively.The AMOVA results showed that 11.99% of the total genetic variance was among the seven collection locations,and among sampling location differentiation was significant.Pairwise Fst ranged from-0.02582-0.39347.Pairwise genetic distance values between all seven sample sites were shown to be not correlated with geographic water distance indicating that more geographically distant site combinations did not produce higher le vels of genetic differentiation.Moreover,a significant correlation was detected,the analysis produced a low.Phylogenetic analysis for U.douglasiae showed strong support for this species forming a monophyletic clade(posterior probability = 1.00)and four haplotypes found in the XN,PY and GJ population(H15,H16,H28 and H29)formed a monophyletic clade(posterior probability = 0.63).Most haplotypes of TH and HZ formed a monophyletic clade,DT,PY and GJ formed a monophyletic clade,and LZ and GJ formed another monophyletic clade.The mismatch distribution of analysis pairwise differences was significantly different from the expected distribution of the expanding population model.Similarly there was a lack of statistical significance of Tajima's D test,and non-significant Fu's FS.Moreover,when all samples were pooled together,Tajima's D and Fu's FS test were not significant.Additionally,the BSPs showed that U.douglasiae has had a stable historical population size with a small recent expansion event occurring between 250000 and 300000 years...