Abstract: Phylogeography study of P. cathayana′ 14 wild populations in Qinghai-Tibet Plateau was developed by using chloroplast DNA markers. The genetic structure and population dynamics were analyzed in order to reveal its evolutionary history during the Quaternary Glaciation to provide theoretical basis for germplasm resource evaluation and genetic protection strategy formulation. The genomic DNA of P. cathayana was extracted, then the atpH-atpI and rbcL fragments of non-coding region were amplified, detected, purified and sequenced. The mutation sites of the combined sequence of cpDNA were counted and 13 haplotypes were identified. Molecular variation analysis showed that genetic variation mainly existed among populations rather than within populations. There was no phylogenetic relationship between haplotypes in this study, and no recent population expansion was detected by bifurcation analysis and neutral detection. There is no significant correlation between genetic distribution and geographical distribution of P. cathayana. This may be due to the existence of multiple micro-shelters in the study area. For example, the Qilian and Hengduan Mountains may be micro-shelters for P.cathayana during the glacial period, and these areas are also the origin centers of population migration and diffusion after the glacial period.

Key words: Populus cathayana, Qinghai-Tibetan Plateau , cpDNA , genetic diversity, glacial refugia