Phylogeography And Genetic Diversity Of Quercus Dentata Thunb Revealed By CpDNA And Nuclear SSR Markers

Quercus dentata Thunb is very important species of trees which belongs to Quercus L.?Fagaceae?.Q.dentata that spread among the southern of China,Korea and Japen constitutes the mountain forest as one of main species.Due to experiencing a long history Q.dentata was a valuable material to study the response of plants to climatic and geological events.In order to know the genetic diversity and genetic structure,we research the phylogeography of Q.dentata based on cpDNA data.In order to fill Q.dentata's phylogeography blank,we explored the genetic structure and genetic diversity of Q.dentata based on cpDNA fragments and nuclear SSR markers to fill phylogeography of Q.dentata blank.We got the following the results according the below aspects.?1?Phylogeography of Q.dentata.A total of 289 individuals?30 populations?of Q.dentata were analyzed by using three chloroplast DNA fragments(psbA-trnH,ycf1,rps16-trnQ.The result of cpDNA showed that there were 23 haplotypes in Q.dentata's populations.The result revealed the higher haplotypes diversity?H_d=0.9113?and nucleotide diversity??=2.58×10-3?of Q.dentata.The regions with high genetic diversity locates in the Changbai Mountains and the Qinling-Bashan Mountains nearby meantime the regions with abundant private haplotypes located in the Qinling-Bashan Mountains.AMOVA analysis indicated the genetic variation mainly occurred between populations?95.03%?.There was no significantly phylogeographical structure(N_ST>G_ST,P>0.05)indicating the geographical isolation factor had little effect on the genetic difference of Q.dentata.All the result of radial Network and the single peak mismatch analysis and the value of Tajima's D showed Quercus dentata underwent the expansive event about 12.8 kyr.The common ancestor was divided two clades about 3.41 Ma based on Maximum Likelihood and Bayesian analysis.These differentiation time of clades were 2.43 Ma and 1.71 Ma respectively.?2?Genetic structure and genetic diversity of Q.dentata.Here,we estimated the population structure and genetic diversity of Quercus dentata Thunb based on 549 individuals from 31 populations using 8 nuclear SSR markers.Then,we explored the relationship of genetic diversity and biogeographical factors.The results indicated that Q.dentata had moderate level of genetic diversity?H_O=0.248,H_E=0.595,PAr=0.030715,Ar=2.870149,N_a=4.891,I=1.184?.The regions with private allele richness locates mainly in the Changbai Mountains and the Qinling-Bashan Mountains nearby.Genetic variation mainly occurred among populations?81.74%?.All populations of Q.dentata was divided into three clusters by the result of Bayesian clustering analysis.However,there was complex mosaic geographical structure among the populations of Q.dentata due to large and asymmetric gene flow.There were some populations experiencing the bottleneck effect by BOTTLENECK analysis.The private allele richness was significantly positively correlated with latitude?R²=0.1297,P=0.042?indicating the tendency of migrating to higher latitudes occurred during Last Glacial Maximum and genetic difference due to adaptation among different populations..?3?Species distribution models?SDMs?and the possible glacial refuge Species distribution models?SDMs?showed that ancestral populations of Q.dentata mainly located in the southern China nearby and the Changbai Mountains during the LIG?Last Interglacial period?and shrunk to the Qinling-Bashan Mountains during the LGM?Last Glacial Maximum?.The result showed the Qinling-Bashan Mountains was the largest glacial refuge.However,Combine the high level of haplotype diversity with the private allele richness,the result showed another glacial refuge was in the Changbai Mountains.According to above evidences,the populations in the Qinling-Bashan Mountains spread meantime the populations in the Changbai Mountains spread around.They converged in the Jiaodong Peninsula and generated more gene flow.There is high level of genetic diversity in the Jiaodong Peninsula,forming the current distribution of Q.dentata gradually.