异叶泽兰的遗传多样性和居群历史动态研究

异叶泽兰属于菊科泽兰属,是该属分布海拔相对较高的植物,分布在青藏高原东部和横断山海拔1700~3000 m的地区。该文利用ycf6-psbM和rpl32-trnL两个叶绿体DNA(cpDNA)片段以及核DNA片段ITS(nITS)作为分子标记,研究了异叶泽兰的遗传多样性及其分布特征,探讨了其居群历史动态。结果表明:(1)叶绿体片段联合分析结果显示,异叶泽兰在物种水平遗传多样性水平不高,单倍型多态性指数(H_d)为0.656,核苷酸多态性(π)为0.00161;而ITS的基因型多态性指数(H d)为0.687,核苷酸多态性(π)为0.00235。(2)cpDNA和nITS分析结果均显示,异叶泽兰居群水平总的遗传多样性大于居群内平均遗传多样性,遗传变异主要发生在居群间,居群间存在明显的遗传分化(cpDNA:G_st=0.679,N_st=0.655,F st=0.655;nITS:G_st=0.543,N_st=0.370,F_st=0.584),但是由于N_st值小于G_st值,因此异叶泽兰的分布不具有明显的谱系地理结构。(3)基于单倍型地理分布以及Network分析推测,横断山区南部(川西南-滇西北)和云南中部可能是异叶泽兰在第四纪冰期时的两个避难所,中性检验和失配分析的结果支持异叶泽兰在冰期后未发生过居群扩张。

Genetic diversity and population demography of Eupatorium heterophyllum(Asteraceae)

Eupatorium heterophyllum,belonging to Eupatorium(Asteraceae),is distributed in the eastern Qinghai-Tibet Plateau and Hengduan mountain,and has relatively high elevation in comparison with those of other species within this genus.A survey of two chloroplast DNA(cpDNA)fragments(ycf6-psbM and rpl32-trnL),and one nuclear DNA fragment ITS(nITS)were carried out to assess the genetic diversity and infer the population demography of E.heterophyllum.The results showed that the haplotype diversity(H d)of combined cpDNA fragments was 0.656,and the nucleotide diversity(π)was 0.00161 at the species level.These two index values of ITS were 0.687 and 0.00235,respectively.All these data showed that E.heterophyllum had relatively low level of genetic diversity.Both cpDNA and ITS data show that the total genetic diversity of E.heterophyllum was higher than the average value of populations,and the genetic variations occurred mainly among populations.Significant genetic differentiation exists among populations(cpDNA:G st=0.679,N st=0.655,F st=0.655;nITS:G st=0.543,N st=0.370,F st=0.584).However,there was no obvious phylogeographical structure occurred in E.heterophyllum(N st