基于ITS序列分析霍山石斛及其近缘物种之间的亲缘关系

Interspecific relationships among Dendrobium huoshanense and its related species based on ITS sequences

通过分析部分石斛属植物的ITS序列,研究霍山石斛与其近缘物种之间的亲缘关系,并分析石斛属的起源及分化时间.从GenBank下载了1种Malaxis属、1种Liparis属的ITS核苷酸序列为外群,27种石斛属的ITS核序列为内群.经比对后序列长度为682 bp,外群及石斛属的A+T含量均高于C+G,其中序列中有416个变异位点.A+T平均含量为46.4%,C+G平均含量为53.6%.从系统发育树中看出内群分为6支,霍山石斛与石斛组中其他物种的亲缘关系最近,与顶叶组的亲缘关系较近,而与Spatulata组、Dendrocoryne组和Latouria组的亲缘关系最远.对石斛属系统发育的分析显示大部分石斛属分组与传统石斛分组相同,与传统石斛分组不同的是顶叶组的鼓槌石斛、叉唇组和瘦轴组的物种都聚类到石斛组,顶叶组小黄花石斛与聚石斛可能应该另立新的石斛组.通过贝叶斯法估算得出石斛属的最近共同祖先时间为21.4109Ma,而石斛组的最近共同祖先时间为16.5522 Ma,组内平均分化时间约为7.3445 Ma.本研究表明石斛组起源于中新世早期,组内分化主要发生在中新世后期,气候的改变可能促使了石斛组内分化.(图1表2参27)

Based on the ITS sequence analysis of various Dendrobium plants,the interspecific relationships between Dendrobium huoshanense and its related species were studied.The origin of Dendrobium and the divergence time between D.huoshanense and other species were also studied.The ITS nucleotide sequences of one species from Malaxis and one species from Liparis were downloaded from GenBank as the outgroup,and 27 Dendrobium species were used as the ingroup.After comparison,the length of the sequence was 682 bp.The A+T content of the outgroup and Dendrobium was higher than the C+G content.There were 416 variable sites throughout the sequences.The average contents of A+T and C+G percentages were 46.4%and 53.6%,respectively.In the phylogenetic tree,the ingroup was divided into six clades.D.huoshanense displayed the closest relationship with other Dendrobium species and a closer relationship with D.chrysotoxum,while it exhibited the furthest relationship with Spatulata,Dendrocoryne,and Latouria.The phylogeny analysis of Dendrobium showed that the grouping of the majority of Dendrobium is the same as that of the traditional Dendrobium.Unlike the traditional groupings,D.chrysotoxum,Stuposa,and Breviflores were clustered in the Dendrobium section.D.jenkinsii and D.lindley were most likely added to members of the new genus Dendrobium.Using the Bayesian method,the most recent common ancestor of Dendrobium was estimated to occur approximately 21.4109 Ma.The section Dendrobium evolved and diversified from the Upper Miocene and Lower Miocene in 16.5522 Ma and 7.3445 Ma,respectively.These results indicate that the Dendrobium Group originated in the early Miocene,and divergence within the groups predominantly occurred in the late Miocene.Climate change may have contributed to the division of the Dendrobium groups.