Phylogeography of the temperate tree species Quercus acutissima in China: Inferences from chloroplast DNA variations

Quercus acutissima is one of the most widespread temperate deciduous tree species in China. To study its phylogeographical pattern and demographic history, three chloroplast DNA fragments (atpB-rbcL, psbA-trnH and trnS-trnG) from 401 individuals representing 30 populations were sequenced. A total of 19 haplotypes were identified, and these showed a weak phylogeographical structure (N_ST = 0.689 > G_ST = 0.630, P > 0.05) at the species level. The Q. acutissima population harboured a high level of genetic diversity (H_T = 0.791), and the genetic variation mainly resided among populations (59.54%). The unimodal mismatch distribution and significantly negative Fu's F_S value indicate that the Q. acutissima population experienced rapid range expansion, which probably occurred between 0.37 and 0.12 Ma. Molecular phylogeography and ecological niche modelling (ENM) data suggest the existence of multiple localized glacial refugia in central China (e.g., the Qinling, Dabashan and Dabieshan mountain ranges) and southwestern China (Yunnan-Guizhou Plateau and its adjacent regions) during the Quaternary glaciations. Our study showed that geographical heterogeneity and climate changes may have shaped the genetic structure and phylogeographical pattern of this tree species in China.