Phylogeography Of Mylabris(Pseudabris) Hingstoni(Coleoptera:Meloidae)

Mylabris(Pseudabris)hingstoni Blair,1927 is endemic to the high-altitude areas of the southern Qinghai-Xizang Plateau.It is an ideal material for studying the effects of geological changes on the Qinghai-Xizang Plateau and climate change during the Pleistocene on the differentiation of insect populations in high altitude areas.In the present thesis,M.hingstoni was used as the research material and collected from Lhasa,Shannan,and Xigazê of Xizang Autonomous Region,which includes 16 counties,40 geographic populations.Three gene fragments,mt DNA(16S,COI)and nuclear gene ITS2,were amplified.By using the method of single gene and genes combined analyses,the population dynamic evolution and the evolutionary path of M.hingstoni were analyzed;the advantages and disadvantages of different molecular markers were discussed.The results provide molecular evidence for the phylogenetic development of this species.These are valuable data for understanding the formation and differentiation of populations on the Qinghai-Xizang Plateau.The details is following:1)In total,693 bp of COI gene fragment,401 bp of 16 S gene fragment,295 bp of ITS2 gene fragment and 1389 bp of 3 genes combination were obtained.The three single-gene sequences and the combined gene sequences of Coleoptera chinensis showed that the content of A+T was higher than that of G+C,which was in line with the characteristics of coleopteran insect gene sequences.In these three fragments,the content of A+T is higher than that of G+C,which is as same as other beetles.In 180 sequences of COI,there were 72 haplotypes;and the haplotype diversity was 0.915.Meanwhile,thirty-five haplotypes were found in 175 sequences of 16 S r DNA;and its haplotype diversity was 0.566.Eight haplotypes were detected in 167 sequences of ITS2;its diversity was 0.127.Furthermore,in the 164 combined sequences,100 haplotypes were tested,and the haplotype diversity was 0.967.It can be seen that the greater the molecular evolution rate and the longer the gene sequence,the higher the haplotype diversity.This research proved again COI is an ideal fragment to analyze population differentiation and a well marker to determine the species and infraspecific taxa.The 16 S and ITS2 gene fragments are not suitable for exploring the phylogenetic relationships among infraspecific taxa but available in the species and the above.2)AMOVA analysis showed that the variation of 16 populations of M.hingstoni occurred within and between the populations,which may be related to geographic distance.The analyses of mismatch distribution,neutrality test,BSP,Max Ent model prediction,and molecular dating,combined with geological events and paleoclimatic changes,show that the differentiation of M.hingstoni and M.longiventris occurred in ca.1.95 Ma when is the active period of the Qingzang movement.After that,M.hingstoni divided into two clades in approximately 0.32 Ma: one clade is mainly distributed in Lhasa and Shannan;the other is mainly distributed in southwestern Xigazê.The bordered areas among Lhasa,Shannan,and Xigazê are the mixed zones of the two clades.This divergence is probably because the Kunhuang movement led to the uplift of the Qinghai-Xizang Plateau and the paleoclimatic change,and its habitat preference and low migration ability.During the Last Glacial Maximum(0.026–0.016 Ma),M.hingstoni retreated to a narrow range of N29° and E88°–90°for refuge the adverse environment.Under the scenario of climate warming in the mid-Holocene(9000–5000 years ago),the species began spreading to western Xigazê.In addition,M.hingstoni westward migrations under the current climate model also warn global climate is warming,which should arouse pe ople's attention.