中国特有森林树种华山松的群体进化历史研究

Evolutionary History of an Endemic Conifer Tree Pinus armandii in China

利用现代分子群体遗传学的分析手段,对华山松27个自然群体129个个体的样本进行双亲遗传核基因AGP6片段的测序分析,检测该物种在第四纪冰期时的避难所和群体进化历史。结果表明:(1)华山松群体在AGP6基因座位上具有较高水平的核苷酸多态性,其沉默位点多样性值(πt=0.013 8,πsil=0.030 6)显著高于其他松属植物。(2)基于Bayesian聚类分析结果表明,华山松具有明显的群体遗传结构,地理分布区上能够分为中国中部和中国西南部两大区域族群,Network网络分析和系统发育分析均得到了相似的结果。(3)分子变异(AMO-VA)分析结果表明,遗传变异主要存在于群体内(65.65%)和族群间(30.18%),群体间存在较小的变异量(4.17%);物种水平和族群水平上的群体错配分析分布均呈多峰模式,说明华山松群体未经历过近期的扩张事件。(4)秦岭山脉和横断山区的群体存在较高水平的单倍型多样性和较多的特有稀有单倍型,进一步结合单倍型间的多样性关系,推测这些区域可能是华山松在第四纪冰期时期的避难所。研究认为,不同避难所地区间长期的地理隔离以及高大山脉、河流等异质性生境的形成可能促使了华山松在中国中部和西南部两大区域族群的异质性分化以及物种较高水平的核苷酸多态性。

In this study,we investigated the population genetic structure and evolutionary history of Pinus armandii and we aim to speculate the refugia of this species during Quaternary ice ages.The bipaternallyinherited nuclear gene AGP6 was utilized to study the genetic variations within and among 27 natural populations (129 individuals) of P.armandii in China.The results showed that:(1) P.armandii have a higher level of nucleotide diversity (π t= 0.013 8,π sil = 0.030 6) than the other Pinus species.(2) Bayesian clustering divided the total samples into two groups:one was from the middle-eastern region and another was the southwestern group in China.Both the Network and phylogenetic analyses supported this conclusion.(3)Analysis of molecular variance (AMOVA) showed that the genetic variation mainly occurred within populations (65.65%) and among groups (30.18%),and only a little genetic variation occurred among populations (4.17%).A strongly multimodal mismatch distribution curve indicated that no recently population expansion took place for this endemic species.(4)Based on the geographic distributions and genetic diversity patterns of AGP6 haplotype,we speculated that P.armandii had several refugia in the Qinling Mountain and the Hengduan Mountain areas.The long-time geographic isolation between different refugium areas and heterogeneous habitats induced by large mountains and rivers may have resulted in the high level of population differentiation.In addition,the distinctly population genetic structure and evolutionary dynamics could be another contributing factor to the high level of nucleotide diversity of P.armandii .