基于叶绿体DNA trnL内含子序列变异的远志谱系地理学研究

目的研究我国自然地理分布范围内远志Polygala tenuifolia的分子谱系地理情况,揭示其地理分布格局的形成原因,推测该物种潜在的冰期避难所及冰期后的迁移扩散路线。方法使用叶绿体非编码片段(trn L内含子序列)对远志在我国自然地理分布区内的39个居群308个个体的遗传变异分布模式进行检测。结果共发现26个多态性位点,得到12种叶绿体单倍型。单倍型系统发育分析显示远志自然居群可划分为南、北2个地理组群:北方(包括中国东北、中部、西北地区)组群和南方组群,南北组群没有共享单倍型。居群遗传结构分析表明2个地理组群之间遗传分化较大(Gst=0.783,P<0.001),物种水平遗传多样性较高(Ht=0.755),北方组群不存在明显的谱系地理结构。结论第四纪冰期时远志在中国北方和南方地区存在多个避难所;冰期后或间冰期,北方地区发生了明显的居群扩张事件;南、北组群的分化可能是由于长期的地理隔离所致。

Phylogeography of Polygala tenuifolia inferred from chloroplast DNA trnL intron sequence variation

Objective To study the molecular phylogeography of natural populations of Polygala tenuifolia (Polygalaceae) in China, reveal the forming reasons of geographic distribution pattern of extent populations, and further determine the potential glacial refuges and colonization/migration routines of P. tenuifolia during the postglacial or interglacial periods. Methods We investigated the distribution patterns of genetic variation of 308 individuals from 39 natural populations of P. tenuifolia in China based on one chloroplast DNA fragment (cpDNA trnL intron). Results A total of 26 polymorphic sites were identified and 12 cpDNA haplotypes were recovered. Phylogenetic analysis of cpDNA haplotypes suggested that the natural populations of P. tenuifolia could be divided into two different groups: northern part (including populations of northeast, center, and northwest of China) and southern part. There were no shared cpDNA haplotypes between the two groups. And the population genetic analysis suggested that the high level of genetic differentiation (G_st = 0.783, P < 0.001) between the two groups, the high level of the genetic diversity were found (H_t = 0.755) at the species level. No significant phylogeographic structure was detected in the North group. Conclusion The present studies revealed that the multiple glacial refuges of P. tenuifolia are identified in the northern and southern parts of China during the Quaternary periods. And northern populations have occurred the expansion events during the post-glacial or interglacial periods. The genetic divergence between the north and south groups of natural populations of P. tenuifolia may be caused by the long term geographic isolation.