Study On Phylogeography And Population Genetics Structure Of Quercus Acutissima Carr.

Quercus acutissima Carr.,which belongs to Quercus L.(Fagaceae),is the dominant species in temperate and subtropical regions of East Asia.This specie distributed in China,Korea,Japan,Vietnam and other countries.In the longitude of 91°-123°E and latitude of 18°-41°N China,these plants have to be optimally adapted to environmental conditions,when weather is changed;they react most sensitively to the environment.It is distributed across a variety of climatic and environmental zones and there are hybrid phenomena between other species,which makes it a great subject to study the impact of climate change on species evolution,species genetic structure and genetic differentiation.Based on the survey of wild field,the genetic structure and genetic diversity of Q.acutissima in the distribution area were studied by using the single parent genetic cpDNA marker and the parental nSSR marker.The current distribution and climate of the species Geological events,simulating its possible habitat during the last ice season and the expansion of the late ice.The main findings are as follows:(1)Joint analysis of chloroplast fragmentsA total of 502 individuals(55 populations)of O.acutissima were analyzed by using four chloroplast DNA fragments(coding region:ycfl,noncoding regions trnD-trnE,psbA-trnH and rps16-trnQ).A total of 26 haplotypes were detected,haplotype diversity Hd=0.7628,nucleotide diversity ?=0.61×103,mean nucleotide difference K =1.079.The genetic diversity of Q.acutissima was slightly higher(HT=0.770)and had a smaller gene flow(Nm=0.12).The results showed a weak phylogeographical structure(NST<GST;p<0.05)at the species level.IBD results showed that there was no significant correlation between genetic distance and geographic distance(r = 0.0353;p>0.05).AMOVA analysis showed that genetic variation was mainly between populations(63.25%),and the variation within the population was small.The mismatch analysis showed that there was a recent expansion of Q.acutissima with an expansion time of about 11.2 kyr.NETWORK and Bayesian analysis were divided into two branches,BEAST calculated the recent common ancestor of Q.aczstissima with differentiation time of about 6.55 million years ago,and the two branches with the differentiation time of about 4.81 million years ago and 3.42 million years ago respectively.The geographical distribution pattern of haplotypes and the genetic diversity of each population suggest that Qinba Mountain,Sichuan Basin,Yunnan-Guizhou Plateau,Wuyi Mountain and Tianmu Mountain area are potential ice shelters for Q.acutissima.(2)Joint analysis of nuclear microsatellite lociA total of 510 individuals(33 populations)of Q.acutissima were analyzed by 10 pairs of nSSR primers.The results showed that the genetic diversity of Q.acutissima was not high(Na = 5.264,Ne = 3.504,I = 1.218,Ho=0.283,He=0.595,PPL = 96.06%).STRUCTURE results were divided into two groups.The TESS results and the UPGMA tree also supported this group.The Mantel test showed no significant correlation between genetic distance and geographical distance(r = 0.138,p>0.05).Genetix analysis showed that 33 populations of Q.acutissima had significant differentiation(p<0.05).The genetic variation was mainly from the population(84.26%)by AMOVA analysis,and the variation among the populations was insignificant.Based on the results of the STRUCTURE grouping,Genetic variation among the populations(82.59%),the variation between groups was only 3.95%.F statistics also showed a small genetic differentiation among populations(FST = 0.203)and a larger gene flow(Nm=1.353).BOTTLENECK analysis showed that some populations experienced a bottleneck effect.Through the analysis of standardized allele abundance and proprietary allele abundance,we found that these indices in the Qinba Mountain,Yunnan-Guizhou Plateau,Wuyi Mountain and Tianmu Mountain areas are higher,possibly the ice age shelter of Q.acutissima;the AIS analysis also supports this hypothesis.In addition,through EDENETWORK,we also found that there is more gene flow between the shelters,suggesting a weak quarantine effect between populations.(3)Niche simulation and ice age shelterChloroplast data and nuclear microsatellite data show that the Q.acutissima has a number of shelters.The niche simulation also shows Qinba Mountain and Yunnan-Guizhou Plateau area might be the quasi-garland quasi-shelter.Combined with these analyzes,we believe that the potential shelter for Q.acutissima is located in the Qinba Mountains and the Yunnan-Guizhou Plateau.After the glacial period,the oak is expanded from the shelter to the surrounding habitat.In the central China,the residents of the sanctuaries are communicated and there may be secondary contact.(4)Protection recommendationsAlthough the oak is widely distributed in China,but this research work found that its diversity level is not very high.The increased effects of human activities and the irrational use of germplasm resources have had a significant impact on the distribution of the activity of Q.acutissima.the present distribution of Q.acutissima had a tendency of fragmentation and mostly for secondary forests.Therefore,we suggested the prohibition of deforestation and to restore the scale of forest.