| Parnassia wightiana Wall.ex Wight et Am.is an ancient species of the genus Parnassia distributed in China-Himalayan region.Its geographical distribution spans the three major plant hotspots in China,showing an obvious disjunct distribution,which is an ideal material for the study of alpine plant phylogeography.At the same time,P.wightiana has great potential in the development of ornamental,medicinal and chemical products.In this study,three chloroplast gene(cp DNA)fragments(rpl32-trn L,trn L-F,trn S-G)and one nuclear gene(n DNA)fragment(ITS)were used to explore the genetic diversity and phylogeographic structure of P.wightiana.Combined with the maximum entropy model(Max Ent),the historical population dynamics,migration routes and refugia locations were speculated by using the environmental variable data of historical periods.The main results are as follows:(1)The total length of the three cp DNA fragments is 1830 bp,55 informative loci and 26 haplotypes were detected,the total genetic diversity Ht=0.885,and the genetic differentiation coefficient Fst=0.962;the length of the ITS fragment was 344 bp,and47 haplotypes were detected Information locus,with 36 haplotypes,total genetic diversity Ht=0.980,genetic differentiation coefficient Fst=0.961;P.wightiana has a phylogenetic structure,the population has not experienced a recent expansion event,and genetic variation mainly exists between populations;(2)The distribution of P.wightiana was consistent with the pattern of ’ glacial expansion-interglacial contraction ’.From the last interglacial period to the present,the distribution range of P.wightiana has remained stable.It was speculated that P.wightiana might travel along the mountains between high altitude and low altitude,and did not show obvious expansion or contraction in the horizontal direction.Multiple refugia may exist in Hengduan Mountains,Wuling Mountains,Qinling Mountains and Daba Mountains;(3)There are two main migration routes,both starting from the Hengduan Mountains in the southeastern part of the Qinghai-Tibet Plateau,one going westward along the Himalayas into the plateau table,all the way to the west of the Qinghai-Tibet Plateau;the other going eastward through the Yunnan-Guizhou Plateau,Wuling Mountains,and then Wushan,Dalou Mountain,etc.migrated northward as a channel,and finally reached the Qinba area. |
