Phylogeography Of Camellia Taliensis And Camellia Crassicolumna Based On Two Chloroplast DNA Sequences

The Camellia L.is the largest genus of the family Theaceae,is endemic to East Asia.The vast majority of species are distributed in the south of the Yangtze River to Yunnan.As the most important group of Camellia,Sect.Thea has enormous economic,pharmaceutical,scientific research and cultural value.As the wild species of the tea plant.The phylogeography study of Camellia taliensis and Camellia crassicolumna can help to understand the evolutionary process of the wild tea plant after the quaternary glaciation,explain the reasons for the formation of the modern distribution pattern.It is significant of the study of the phylogenetic relationships among Sect.Thea.In this study,the chloroplast fragments rpl32-trnL and trnG-trnS sequences were used to detect genetic diversity and population genetic structure based on 258 individuals from 27 populations of Camellia taliensis and Camellia crassicolumna.We investigated the genetic relationship between the two species and speculated a possible rounte of the glacial refuge and interglacial diffusion for the two species.The main findings are as follows:1.A combined analysis of the chloroplast genome fragments rpl32-trnL and trnG-trnS showed that a total length of 2233-2266 bp after splicing,including 41 mutation sites.A total of 20 haplotypes were detected and all other populations had only a single haplotype,except for the presence of two haplotypes within the CtFQ of Camellia taliensis.H3 is the most widely haplotype,which exist in 3 populations of Camellia taliensis and 2 populations of Camellia crassicolumna.It is the only shared haplotype within the two species.In addition,the shared haplotypes among species populations are H1、H8 and H10.2.Haplotype polymorphism of Camellia taliensis(Hd=0.844)and Camellia crassicolumna(Hd=0.881)were higher than the average level of the plant.AMOVA analysis showed that at the level of plant species,genetic variation occurred mainly within the population(94.83%)with a significant level(Fst=0.99727,p<0.001),revealing that the genetic variation of the two species is mainly found in species and extremely high population differentiation exist.Moreover,the gene flow within species is less than 1,implying that serious genetic communication obstacles exist within the population.3.According to the distribution of ancient haplotype H3 and transitional haplotype H13,combined with geological and historical events,Pingbian areas have become natural refuge for the species because of their history of not being affected by quaternary glaciers.The horizontal and vertical valleys of the Hengduan Mountains are glacial refuge.In terms of the Ailao Mountain-Wuliang Mountain boundary,the H3 are symmetrically distributed,the H13 and H6、H7、H8、H11H12 are diagonally distributed,the distribution of 3 populations of Camellia taliensis which shares one haplotype along the left side of the sector.In summary,it can verify the authenticity of this possible geographical division of the “Tanaka Line” to a certain degree.4.In combination with geographical geological events,two possible diffusion pathways have been inferred.One is spread to the northeast and west along the Yuanjiang River and Ailao Mountain-Wuliang Mountain by the diffusion neutral position of Pingbian and Jinping areas,the other is spread northwards along the Sanjiang River Basin and the southern of the Hengduan Mountain by the diffusion neutral position of the vertical and horizontal valleys of the Hengduan Mountains.