title: The phylogeography of Fagus hayatae (Fagaceae): genetic isolation among populations.
abstract: The beech species Fagus hayatae is an important relict tree species in subtropical China, whose biogeographical patterns may reflect floral responses to climate change in this region during the Quaternary. Previous studies have revealed phylogeography for three of the four Fagus species in China, but study on F. hayatae, the most sparsely distributed of these species, is still lacking. Here, molecular methods based on eight simple sequence repeat (SSR) loci of nuclear DNA (nDNA) and three chloroplast DNA (cpDNA) sequences were applied for analyses of genetic diversity and structure in 375 samples from 14 F. hayatae populations across its whole range. Both nDNA and cpDNA indicated a high level of genetic diversity in this species. Significant fixation indexes and departures from the Hardy-Weinberg equilibrium, with a genetic differentiation parameter of R st of 0.233, were detected in nDNA SSR loci among populations, especially those on Taiwan Island, indicating strong geographic partitioning. The populations were classified into two clusters, without a prominent signal of isolation-by-distance. For the 15 haplotypes detected in the cpDNA sequence fragments, there was a high genetic differentiation parameter (G st = 0.712) among populations. A high G st of 0.829 was also detected outside but not within the Sichuan Basin. Consistent with other Fagus species in China, no recent population expansion was detected from tests of neutrality and mismatch distribution analysis. Overall, genetic isolation with limited gene flow was prominent for this species and significant phylogeographic structures existed across its range except for those inside the Sichuan Basin. Our study suggested long-term geographic isolation in F. hayatae with limited population admixture and the existence of multiple refugia in the mountainous regions of the Sichuan Basin and southeast China during the Quaternary. These results may provide useful information critical for the conservation of F. hayatae and other Chinese beech species.
authors.affiliation: Department of Ecology College of Urban and Environmental Sciences The MOE Key Laboratory of Earth Surface Processes Peking University Beijing 100871 China.
authors.forename: Ling-Xiao
authors.initials: LX
authors.lastname: Ying
authors.affiliation: School of Life Sciences Peking-Tsinghua Center for Life Sciences Peking University Beijing 100871 China.
authors.forename: Ting-Ting
authors.initials: TT
authors.lastname: Zhang
authors.affiliation: Experimental Forest/Department of Forestry National Chung Hsing University 250 Kuokuang Rd. Taichung 40227.
authors.forename: Ching-An
authors.initials: CA
authors.lastname: Chiu
authors.affiliation: Department of Forestry and Natural Resources National Ilan University 1 Sec. 1 Shen-Lung Road I-Lan 260.
authors.forename: Tze-Ying
authors.initials: TY
authors.lastname: Chen
authors.affiliation: School of Life Sciences Peking-Tsinghua Center for Life Sciences Peking University Beijing 100871 China.
authors.forename: Shu-Jin
authors.initials: SJ
authors.lastname: Luo
authors.affiliation: College of Natural Resource and Environment East China Normal University Shanghai 200062 China.
authors.forename: Xiao-Yong
authors.initials: XY
authors.lastname: Chen
authors.affiliation: Department of Ecology College of Urban and Environmental Sciences The MOE Key Laboratory of Earth Surface Processes Peking University Beijing 100871 China.
authors.forename: Ze-Hao
authors.initials: ZH
authors.lastname: Shen
keywords: Fagus hayatae; cpDNA sequence fragments; genetic isolation; nDNA SSR loci; phylogeography