Population Genetics Of Quercus Aliena Based On CpDNA And SSR Marker

Quercus aliena Blume is one of the main mountain tree species of subtropical and temperate forest in China,which has significantly ecological and economic values.However,the study of population genetics and phylogeography for Q.aliena is still underestimated.In order to reveal the geographical structure,population dynamics in the process of evolution,genetic diversity,genetic structure and their associations with mountain habitat of the species,52 populations with 500 individuals of Q.aliena were firstly analyzed in phylogeography based on three cpDNA(ycf1,rps16-trnQ?psbA-trnH).According to the phylogeographic results,we selected 23 populations with 461 individuals from the 52 populations to investigate the genetic structure of Q.aliena with 10 pairs of nuclear SSR primers.The main results are listed as follows:The haplotype result of cpDNA showedthat there were a total of 33 haplotypes in Q.aliena populations,while Hap3 was the ancestral haplotype.The results indicated higher haplotypes diversity(Hd=0.897)and nucleotide diversity(?=0.00206)of the species at the species level.AMOVA analysis revealed that genetic variation of chloroplast genes mainly existed among populations(among populations was 82.66%,within populations was 17.67%).Furthermore,Q.aliena possessed significant population genetic differentiation(FST=0.8433).No significant geographical structure was found among Q.aliena populations(NST>GST,P>0.05).Correlation analysis of genetic and geographic distances using Mantel test also showed no significant correlation between genetic and geographic distances(r = 0.125,P = 0.100).Besides,the result of Network and the haplotypes distribution of Q.aliena indicated that the Hengduan Mountain and Qinling-Bashan Mountains comprised many unique and ancestral haplotypes as well as abundant haplotype diversity,where might be as glacial refugia during the Quaternary period.Both mismatch distribution analysis and species distribution modelling(SDM)of Q.aliena implied that the species had experienced population expansion,and the expansion event might have taken place after the glacial period.After the glacial period of Quaternary,population of Q.aliena may moveto the east and to the northeast through two migration and expansion ways,respectively.The result of SSR marker indicated rich genetic diversity(Ne=2.744,I=1.077,H0=0.290,PPL=95.22%)of Q.aliena,while diverse genetic diversity was found among differernt populations.The genetic variation mainly existed within populations and population differentiation was relatively low in this species(FST=0.1734,P<0.001),as revealed by the analysis of moleculer variance(AMOVA).23 populations could be divided into two clusters by the Bayesian clustering analysis(STRUCTURE).F-statistics showed that genetic differentiation among populations of Q.aliena was low(FST=0.022).For the 23 populations of Q.aliena,correlation analysis of genetic and geographic distance using Mantel test also showed no significant correlation between the two distances(r = 0,125,P = 0.100).Some populations had experienced bottleneck events during the species history,and the Barrier test also indicated that genetic barriers existed among some populations.EDENetwork analysis revealed that gene flow were frequent among populations;The genetic diversity of populations along the Hengduan Mountains and Qinling-Bashan Mountains was high based on the nSSR results.We speculated that these mountains might be potential refugia during the glacial period.After glacial period,Q.aliena expanded from refuges to the surrounding areasto seek for suitable environments.