基于5.8SrDNA/ITS序列的内蒙古棘豆属植物分子系统学分析

对12种34个地理种群的内蒙古棘豆属植物核糖体ITS区段和5.8S基因序列进行比较分析,并采用Maximum Likelihood法构建系统发育树.结果表明:支持棘豆属植物为单系起源,支持《内蒙古植物志》将黄毛棘豆(Oxytropis ochrantha)、多叶棘豆(O.verticillaris)、二色棘豆(O.bicolor)和砂珍棘豆(O.racemosa)归入真棘豆亚属(Subgen.Euoxytropis)轮叶棘豆组(Sect.Baicalia Stell.ex Bunge)的观点.推测多叶棘豆和砂珍棘豆ITS2区段出现的C/T转换可能是其部分种群混杂在其他物种中的主要原因,但基因转换对于系统发育的影响仍尚未可知.研究不支持传统分类学上对鳞萼棘豆(O.squammulosa)与刺叶柄棘豆(O.aci ph ylla)的划分,系统发育树显示二者聚为一支,而非与传统分类学上界定的同组或同亚属植物形成一支；结合植物地理学研究结果,认为刺叶柄棘豆与鳞萼棘豆为地理替代种.推测刺叶柄棘豆可能为多系起源物种.线叶棘豆(O.fili formis)和东北棘豆(O.coerulea与真棘豆亚属物种构成姐妹群,而非单室棘豆亚属植物.研究认为在物种界定过程中,只将少数几个形态学特征作为主要分类依据欠妥.

Molecular Phylogenetic Analysis of Several Oxytropis DC.Speciesin Inner Mongolia Based on 5.8SrDNA/ITS Sequences

In this research,the phylogenetic relationships among genus Oxytrpis in Inner Mongolia were analyzed by comparing their internal transcribed spacers(ITS) and 5.8S gene of nuclear ribosomal DNA sequences.The phylogenetic tree was constructed by Maximum Likelihood method with MEGA 5.0 software.The molecular data supports that Oxytropis was monophyletic taxon.The results were congruence with Flora of Intromongolica consensus which put Oxytropis ochrantha,O.verticillaris,O.bicolor and O.racemosa into Sect.Baicalia.C/T transition may be the main reason for the mixture of populations of O.verticillaris and O.racemosa,but the effects of this base transition on phylogeny to these species are unknown.The results provided no support for classification of O.squammulosa and O.aciphylla.However,they were actually showed close to each other,rather than clustered in different subgenera.Furthermore,we presumed that O.aciphylla was a polyphyletic taxon.In conjunction with the earlier studies of floristic geography,we suggested that O.aciphylla and O.squammulosa were geographical substitute species.The results showed that O.filiformis and O.coerulea was sister to Subgen.Euoxytropis species,instead of clustering with Subgen.Phacoxytropis species.We also proposed that it was unreasonable to consider only several morphological characters in identifying species.