Phylogeography of Saxifraga egregia in Himalaya-Hengduan Mountains

doi:10.7525/j.issn.1673-5102.2018.05.002

Abstract

Abstract: The experiment was conducted to studygenetic structure and phylogeographic history of Saxifraga egregia, by using two chloroplast DNA sequences, rpl20-rps12 and trnL-trnF, and a sampling strategy of 151 individuals from 13 populations in the Himalaya-Hengduan Mountains. Nineteen haplotypes(H1-H19) were detected based on the concatenated sequences of rpl20-rps12 and trnL-trnF. Haplotype H2 was wide-spread across the distribution range of S.egregia, while 63% were private haplotypes. Genetic structure analysis detected a high level of total gene diversity(H_t=0.868), however, average within-population diversity was relatively low(H_s=0.466).By analysis of molecular variance, 57.37% of the total variation was described as within-population variation, while among-population variation was represented as 42.63%. An estimation of non-significantly larger N_st(0.463) than G_st(0.438,P>0.05) value suggested an absence of phylogeographic structure across the whole distribution range of S.egregia. Recent range expansion or demographic expansion at the level of total gene pool of S.egregia were rejected according to neutrality tests and mismatch distribution analysis. Genetic signal of a stochastic distribution of private haplotypes, as well as populations with high gene diversity and nucleotide diversity, suggesting the existence of multi-microrefugia of S.egregia during Quaternary glaciations. Repeated expansion and contraction of distribution range of S.egregia during Quaternary glaciations could have finally fragmented its distribution range into isolated "alpine islands", and have facilitated allopatric divergence, resulting in the formation of high proportion of private haplotypes across the distribution range of S.egregia. It has been reported that some trees and shrubs inhabited by S.egregia showed multi microrefugiain the Qinghai-Tibetan Plateau during Quaternary glaciations, which may have provided suitable micro-environment for the in situ survival of S.egregia during glacials.

Key words: Saxifraga egregia, Himalaya-Hengduan Mountains, phylogeography, microrefugia

CLC Number:

Q949.751.2

JIA Liu-Kun, JIAO Xiu-Jie, LIU Hai-Rui, LI Yan, GENGJI Zhuo-Ma, WANG Zhi-Hua, GAO Qing-Bo. Phylogeography of Saxifraga egregia in Himalaya-Hengduan Mountains[J]. Bulletin of Botanical Research, 2018, 38(5): 644-652.

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