Phylogeography Of Chloroplast DNA Variation In Ginkgo Biloba

We examined the phylogeography of 7 potential wild populations of Ginkgo biloba L. from Yungui Plateau, Dabie Mountains and Funiu Mountains, and West Tianmu Mountain in China to determine the Genetic structure of Ginkgo populations, and to infer the glacial refugia of Ginkgo survived Quaternary ice ages.By sequencing 3 cpDNA intergenetic spacer fragments (trnL-trnF, trnS-trnG and psbB-psbF) and 1 gene region (matK) using universal primers of Ginkgo samples from 7 populations, we found a total of 5 polymorphic sites over 3676 bp. Low nucleotide diversity (0.136%) was found indicating a bottleneck effect during ice ages. Only three haplotypes (HI, HII and HIII) were found in the present study, with the frequencies of being 92%, 2% and 6% respectively. All the individuals bearing haplotype HIII were restricted in the population of Jinfo Mountain and one individual bearing haplotype HII was found in Tianmu Mountain population.Genetic structure was analyzed using nested clade analysis (NCA). Contingency test suggested a significant relation between haplotype HIII and geographic distribution. Nested cladistic distance patterns indicated that restricted gene flow played a vital role in the distribution of haplotype HII, and the most common haplotype (HI) was the ancestral haplotype, and restricted gene flow existed between each distribution, nearly 50% samples of Jinfo mountain population had the same unique haplotype which dispersed limitedly.Analysis combined with three haplotypes reported from Taiwan, Germany and Australia supported haplotype HI being the ancestral haplotype. It indicated that, besides Jinfo Mountain, there were other Ginkgo's refugias which had not sampled in the present study or might be destroyed.The above results indicate that the population history and dispersal process postglacial may consist of two parts. Firstly, one of the glacial legacy existed in Jinfo Mountain which population did not disperse widely postglacial. Secondly, there should be several glacial legacy scattered in China. And some Ginkgo were planted to other countries and areas before wild dispersal occurred, but some populations of refugia expanded, some lost.