Phylogeography Of Stipa Krylovii Based On Chloroplast DNA Sequence

Stipa krylovii Roshev.?Gramineae?is a perennial xerophyte.It is major dominant species of typical Eurasian steppe.Because of it's adaptability to arid environment and wide distribution,it become a bridge connecting the eastern and western steppes and close species of Stipa.The study on the phylogeography of S.krylovii to explore the formation and evolution of typical temperate steppe,enrich the theory of phylogeography of herbage in arid and semi-arid areas and protect the biodiversity of Stipa steppe are of great significance.In this study,we used three chloroplast DNA fragments?rbcL,trnL-F,trnH-psbA?to analyze the phylogeographic structure,genetic diversity,divergence time and population demographic history of 372 individuals in 30 populations of S.krylovii in Mongolia Plateau,Qinghai Tibet Plateau,Tianshan and Altai Mountains in Xinjiang.In addition,we also used species distribution model?MAXENT?to discuss the potential refuge of S.krylovii in Quaternary glacial and the migration route in the post glacial.The main results are as follows:1)12 mutation sites and 9 haplotypes were detected chloroplast fragments in 30populations of S.krylovii based on the concatenated chloroplast sequences.At chloroplast DNA level,low level of genetic differentiation among populations(G_ST=0.12)and high level of gene flow were tested?Nm=1.84?,which genetic diversity of S.krylovii is lower?H_T=0.225,H_S=0.206?and the genetic variation is mainly within the population.2)There was no significant correlation between genetic distance and geographical distance of S.krylovii.The differentiation of S.krylovii phylogenetic is small,and there is no obvious phylogeographic structure(G_ST=0.109,N_ST=0.084,p>0.05).3)The late Tertiary is an important node for the differentiation of S.krylovii.The divergence time of ancestor is 2.77Ma and the haplotype differentiation began to appear in the 1.91Ma.H8 appears in 1.08Ma.4)The population of S.krylovii has experienced expansion in the interglacial period of 0.28 Ma.In the last glacial maximum,it moved southward on a large scale.Yin Mountains,Qilian Mountains,Altai Mountains et al formed a continuous refuge during the glacial period and provided provenance for migration of S.krylovii to the northward in the interglacial period.After the last glacial maximum,until the middle Holocene,there was a large-scale population expansion to the Mongolian Plateau,which formed a spatial distribution consistent with modern one.