基于ITS和trnL-F序列的青藏高原棘豆属植物分子系统学研究

摘要

【目的】探讨青藏高原棘豆属植物的系统学关系,为该属植物的研究提供分子系统学方面的资料。【方法】以青藏高原16种棘豆属植物27个地理种群标本为试材,提取其总DNA后,分别对ITS序列和trnL-F序列进行PCR扩增、纯化及测序,并对所测序列进行同源性比对,用Kimura 2-parameter距离模型计算各序列间的进化距离,以乌拉特黄耆（Astragalus hoantchy）和多枝黄耆（A.polycladus）为外类群,利用MEGA软件构建基于ITS序列和trnL-F序列的青藏高原棘豆属植物的系统发育进化树。【结果】ITS序列对位后长度为710bp,有58个简约信息位点,G＋C平均含量为54.3%,该序列的平均进化距离为0.016,但进化距离总体较小。trnL-F序列对位后长度为867bp,有94个简约信息位点,G＋C平均含量为33.7%,该序列的平均进化距离为0.018,总体进化距离较ITS序列大。ITS序列较叶绿体trnL-F序列含有较多的系统发育信息。在基于2个序列构建的系统发育树中,大花棘豆亚属除少数居群外均形成单系分支,说明以心皮有无隔膜来划分棘豆属属下分类系统可以较好地获得分子系统学的支持;但在其他亚属及组水平上,并不构成单系。【结论】棘豆属各类群间系统发育信息含量明显较低,说明棘豆属物种分化发生较晚,尤其是在青藏高原这样一个始于第三纪造山运动的年轻区域,其棘豆属物种的新近起源和形态的快速分化还难以在遗传水平上固定下来。%【Objective】 The research explored the phylogenetic relationships of Oxytropis DC.of Qinghai-Tibetan Plateau to provide more information for the molecular phylogeny of Oxytropis DC.【Method】 Total DNA of 16 species（27 sequence accessions） of the genus Oxytropis from Qinghai-Tibetan Plateau was extracted,and the ITS sequence and trnL-F sequence were respectively amplified and sequenced,then the homology of the sequences was compared.The evolutionary distance of ITS and trnL-F sequences were respectively calculated by Kimura 2-parameter model.The phylogenetic trees were constructed with the MEGA software and Astragalus hoantchy and A.polycladus were outgroups.【Result】 The aligned length of ITS sequence is 710 bp,and there are 58 parsimonious informative sites and 54.3% G＋C content in the ITS sequence.The average evolutionary distance of ITS sequence is 0.016,but the general distance is small.The aligned length of trnL-F sequence is 867 bp,and there are 94 parsimonious informative sites and 33.7% G＋C content in the trnL-F sequence.The average evolutionary distance of trnL-F sequence is 0.018,but the general distance is more than the ITS sequence.ITS sequence contains more phylogenetic information than trnL-F sequence.On the phylogenetic trees of ITS and trnL-F sequences,Orobia（Bunge） C.W.Chang form a well supported clade.The results suggested that whether having septum in the carpel or not is a good character for infrageneric classification of Oxytropis.However,in the level of other subgenus and sections,the two trees contain low phylogenetic information,and the sections can not form monophyletic group.【Conclusion】 The low phylogenetic information revealed that species differentiation of Oxytropis may be late,especially in the young floristic region like Qinghai-Tibetan Plateau which was formed by Tertiary orogenic movement,circumscription of those species needs further investigation by more data.