Flying over phylogeographic breaks by wind: Quaternary evolutionary history of a mountain aspen in southwestern China

<p>The role of phylogeographic break and wind direction in the formation of plant genetic pattern has aroused increasing interest. Two phylogeographic breaks, MSD and TKL, existed in the Sino-Japanese floristic region have affected many plants, but there was no landscape genetic research across these two phylogeographic breaks. Here, we tested the internal and external factors that influence the phylogeographic pattern of <i>Populus</i> <i>rotundifolia</i>. Genetic variation was surveyed across 49 populations (567 individuals) covering the Chinese range of <i>P.</i> <i>rotundifolia</i>, using 14 nSSRs and 4 cpDNA markers. Demographic and migration hypotheses were tested using coalescent-based approaches, and the current and past potential distributions were predicted using ecological niche modelling. The range and habitat of the western and eastern lineages barely overlap at present, and demographic inferences suggest a population expansion event of <i>P. rotundifolia</i> in 600 Ka. Based on two biogeographic barriers (MSD and TKL) and genetic variation pattern, <i>P. rotundifolia </i>was divided into three groups. The historical gene flow was detected in the central group with western and eastern respectively, indicating an obvious lineages admixture in the central. Moreover, the central part is also the intersection of East Asian monsoon and South Asian monsoon, and has the highest genetic diversity. The existing genetic distribution pattern of <i>P</i><i>.</i> <i>rotundifolia</i> reflects the combined impacts of biogeographic history and biological traits.</p>