Studies On Geographic Boundary Of Pinus Tabuliformis Carr. And P.henryi Mast. Based On CpSSR With Landscape Genetic Analysis

Pimus tabuliformis Carr.and Pinus henryi Mast.,two endemic species,are predominant trees of the coniferous forest in northchina and centralchina,.They are separated by Qinling-Daba Mountains,where ecological substitution of each other is quite unique. However,their landscape boundary was always in discussion.In this study,the spatial genetic structure and the landscape boundary of them were illustrated with landscape genetic statistics.The genetic diversity and divergence of 29 populations,766 individuals were analyzed at both total and population level by using chloroplast microsatellites(cpSSR).Neighbor-join(NJ) dendrogram and Principal Component Analysis(PCA) were used to illustrate the genetic relationships among P.tabuliformis and P.henryi populations.The spatial structure in the cpDNA datasets was inferred with SAMOVA,based on a simulated annealing procedure which aims to maximize the proportion of total genetic variance due to differences between groups of populations.The maximum difference algorithm of Monmonier was applied to identify zones of gene discontinuity.The results showed that at population level the genetic diversity was moderate with a wide range(0.308-0.000),but genetic divgence among populations was quite high(Gst=0.737).R_ST was significantly higher than G_ST,which indicated an existing geographic structure.NJ dendrogram showed two distinct clades indictive of P.tabuliformis and P.henryi,respectively, which was consistent with the result of PCA.For SAMOVA,we repeated the analysis by increasing the value of K until the F_CT value reached a plateau 0.144 at K=3,with 52.54 percentage of the total variation between populations.Hanjiang river,Ren river,Yangzi river and some valleys were identified the barrier of gene flow.Mental test and NCPA indicated that the genetic structure was not the result of isolation by distance,but rather small population size,the inferred worse pollination phenophases,allopatric fragmentation,past gradual range expansion followed by fragmentation or a past larger range followed by extinction in intermediate areas.It was confirmed that P.tabuliformis and P.henryi are indeed two separate species,and the dividing line of geographic distribution between them is located in the Micang Mountain to the Daba Mountain,but the two pines were mixed in Jianliang,Taoyuan and Shuangyang.P.tabuliformis,mainly distributed north of Qinling mountains,is adapted to warm temperate climate;P.henryi,mainly distributed in Daba Mountains,is adapted to semi-tropical climate. Identification the landscape boundary of them will provide implications in both of Qinling-Huaihe climate zone and deme dividing.For the first time,landscape genetic analysis was applied to research of geographic boundary of P.tabuliformis and P.henryi and the results will give insight into researches of ecological-climate transformation all around.