Genetic Diversity And Phylogeographical Studies Of The Tylototriton Taliangensis

Tylototriton taliangensis belongs to Tylototriton of Salamandridae,which is the endemic species in China and only can be founded in the Daliangshan Mountains,located in the southwest of Sichuan.118 samples from 7 geographical populations in Sichuan Province were collected in this study.We use three mitochondrial DNA fragments as molecular markers to evaluate the population genetic diversity,population structure and evolution history of T.taliangensis.The main results summarized as follows:Total of 2,820 bp mtDNA gene fragment was amplified,while,the length of the fragment was ND1-ND2,990 bp,COI,508 bp,D-LOOP,1,322 bp.There were 119 mutation sites in the sequence fragment,and defined 32 haplotypes.The nucleotide diversity(Pi)and haplotype diversity(Hd)were 0.0113 and 0.89 respectively.At the mean time,BI tree and ML tree are estabilished based on haplotype sequence,it can be seen that the topological structure of BI tree and ML tree is similar except for a few nodes with low support.In addition,thirty-two haplotypes can be divided into five major branches,and a wide range of haplotypes of the same geographical population are found clustered in different branches.It is speculated that there has been isolated by geography barrier following by secondary contact between the populations of T.taliangensis.Then,analysis of molecular variation analysis(AMOVA)showed that the mitochondrial genetic variation mainly existed between groups(76.09%),while the difference between populations was small(28.30%),which mean the population of T.taliangensis had a strong geographical structure.The molecular clock analysis indicate that the divergence of the clades occurred in the early Pleistocene from 2.57 Mya to 1.39 Mya thus the topographic fragmentation and Pleistocene glacial cycles in the Daliangshan area caused by the uplift of the Qinghai-Tibet Plateau may be responsible for the population differentiation of the T.taliangensis.Moreover,neutral test and mismatch analysis showed that there was no rapid expansion in the history of each branch and the effective population remained stable for a long time.However,after the Bayesian skyline plot method was used to calculate the population dynamics,a recent decline in the effective population of EB and MG was fund and it may be related to local villagers' activities.Our survey found that the population T.taliangensis was affected by human capture and habitat destruction,and some populations showed a downward trend.To protect the population of T.taliangensis and its genetic diversity,it is necessary to carry out more detailed sampling research,strengthen protection publicity and market supervision,and in the future planning of the protected area of the Daliangshan,the structural characteristics of the population of T.taliangensis should be considered comprehensively to protect their ecological environment.