Molecular Phylogeographic Study Of Stipa Breviflora

In present study, we reconstructed the phylogeographic structure of stipa breviflora using maternally inherited chloroplast (cpDNA) fragments, trying to clarify the influence of Quaternary climate oscillation on grassland forming in arid areas, vegetation distribution and the interspecies genetic divergence. We collected 11 populations of 165 individuals from Inner Mongolian Plateau, Ordos Plateau, Loess Plateau and Sinkiang, to construct phylogenetic structure and history demography of stipa breviflora by utilizing sequences variation patterns of maternally inherited chloroplast DNA (cp DNA). The results showed that:1. In total, there are 41 haplotypes from rich variation loci of two cpDNA fragments, and mainly divided into three phylogene lineages. The populations distributed in the Inner Mongolian Plateau beard the highest population haplotype diversity and most likely occurred genetic admixture, and diverged with populations distributed in the Sinkiang. According to the analysis, the larger divergence between populations occurred (Fst=0.66167), and less gene flow existed.2. Stipa breviflora has a significant geographical structure. There likely to be two original and divergent center, namely the eastern Inner Mongolian Plateau and the Sinkiang region. More importantly, the population demography analysis indicated the population of stipa breviflora was stable. However, populations from the Inner Mongolian Plateau might recently expanded. BEAST analysis showed that the genetic divergence occurred at～0.96 Ma between the Sinkiang and the other two clusters,～0.57 Ma between the Inner Mongolian Plateau and Loess Plateau.3. Ecological niche modeling (ENM) was constructed for the arid grassland constructive species to understand its distribution range during Last Glacial Maximum (LGM) and Last Interglacial (LIG) periods. The results showed that stipa breviflora have been distributed in the LIG period and expanded from LGM to the present, which suggested the population expansion was related with global climate drier and colder during LGM period, while the climate of north China is steering to be warm and wet during the last deglaciation, the condition of which was not suitable for the species survival, leading to be rapidly migrated and dispersal. Hence, although the origin time was rather late, the populations dispersed very fast. Population expansion of the stipa breviflora affected by Pleistocene climate oscillation suggested that the range of the desert-steppe will obviously expansion in the future.