唐古特虎耳草谱系地理学研究

Phylogeography of Saxifraga tangutica Engl. (Saxifragaceae)

利用叶绿体基因(trnL-trnF和rpl16)对青藏高原地区的18个唐古特虎耳草(Saxifraga tangutica Engl.)居群(209个个体)进行谱系地理学研究,以揭示唐古特虎耳草的现有遗传结构及其历史演化过程。结果表明:(1)从209个个体中共检测到74个单倍型,且只有单倍型H5在居群中广泛分布,71.62%的单倍型为居群特有单倍型。(2)分子变异分析(AMOVA)显示,91.85%的遗传变异来源于居群内,居群间遗传分化不明显(F_(ST)=0.081);遗传分化系数N_(ST)(0.109)大于G_(ST)(0.097,P>0.05)但不显著,表明唐古特虎耳草在其整个分布范围内没有明显的谱系地理结构。(3)中性检验表明,Tajima’s D(-2.045 07,P<0.05)和Fu&Li’D*值(-3.629 27,P<0.05)均为显著的负值,结合单峰的错配分布曲线,表明该物种经历过近期扩张。研究推测,唐古特虎耳草在第四纪冰期时可能存在多个微型避难所,由于第四纪冰期气候的反复波动,使得原来连续的居群片段化,避难所内的居群单独进化,从而形成了大量特有单倍型;唐古特虎耳草居群对第四纪冰期气候波动的反应可能更多的表现为垂直海拔高度的迁移,而非大规模的水平迁移。

Two chloroplast DNA intergenic spacers,trn L-trn F and rpl16,were employed to study phylogeography of Saxifraga tangutica,which aimed to explore genetic structure and phylogeographical history of this species.The result showed that:(1)based on range-wide sampling(18populations and209individuals),we detected74haplotypes.Only one haplotype(H5)was widespread,while71.62%were private haplotypes,i.e.,observed in single populations.(2)Analysis of molecular variance showed that within-population variation was described as91.85%of the total variation,while among-population variation was not distinct(F ST=0.081).An estimation of non-significantly larger N ST(0.109)than G ST(0.097,P>0.05)value across all populations suggested an absence of phylogeographical structure across the whole distribution range.(3)Neutrality tests of Tajima s D(-2.04507,P<0.05)and Fu&Li D*(-3.62927,P<0.05)showed significantly negative values,in combination with unimodal of mismatch distribution analysis,suggested a recent demographic expansion of S.tangutica.Based on results given above,we speculated that there might be multi microrefugia for S.tangutica on the Qinghai-Tibetan Plateau platform during Quaternary glaciations.Climatic oscillations during Quaternary glaciations fragmented the distribution range of S.tangutica into isolated populations,subsequent allopatric divergence resulted in the formation of numerous private haplotypes across its distribution range.Populations of S.tangutica possibly experienced in situ altitudinal migrations to respond glacial and interglacial intervals,instead of extensively horizontal migration.