近日,由中国科学院昆明植物研究所孙航研究员带领的课题组,在国家重点基础研究发展计划(973)(2007CB411601)和国家自然科学基金(30625004, 40930209, 31000101)等项目的资助下,对分布在青藏高原—喜马拉雅地区的绢毛苣属(Soroseris)、肉菊属(Stebbinsia)与合头菊属(Syncalathium)植物进行了分子系统发育和生物地理学研究,其目的在于探究青藏高原地区植物的物种成因以及进化模式。
菊科绢毛苣属、肉菊属与合头菊属为主要分布于青藏高原高海拔地区的特有类群。本研究利用ITS,trnL-F和psbA-trnH对三属植物进了分子系统学分析和生物地理学探讨,分析结果表明,肉菊应该归并于绢毛苣属,而合头菊属分为两支:狭义合头菊属(Syncalathium s.str.)与康滇合头菊(Syncalathium souliei),前者位于还阳参亚族,而后者位于莴苣亚族并与广义莴苣属亲缘,所以康滇合头菊应该作为Lactuca souliei放回原广义莴苣属,具体分类学处理将另行发表(新属-假合头菊属Parasyncalathium)。
研究同时发现,这些类群在此区域存在着三种进化模式,如绢毛苣属为一快速辐射进化而成的类群;狭义合头菊属为替代分布,进而发现其具有异域分化进程,本属可能是从青藏高原东北部的甘肃、青海和四川逐步向青藏高原腹地演化;而狭义合头菊属与康滇合头菊间由于同处于青藏高原恶劣的生态环境选择压力和气候变化,进而存在形态趋同进化模式。生物地理学研究发现,广义绢毛苣属和原合头菊属均为年轻的分化类群,其大概起源和分化时间为1.56—8.44百万年前;结合地质学资料和现有系统学研究结果推断,这些年轻类群应该是在青藏高原的隆升过程中随着环境的变化和流石滩生境的破碎化而形成。
该研究成果已在2011年出版的Taxon期刊上发表。(生物谷Bioon.com)
生物谷推荐原文出处:
Taxon, Volume 60, Number 1, February 2011 , pp. 15-26(12)
Molecular phylogeny and biogeography of three closely related genera, Soroseris, Stebbinsia, and Syncalathium (Asteraceae, Cichorieae), endemic to the Tibetan Plateau, SW China
Zhang, Jian-Wen; Nie, Ze-Long; Wen, Jun; Sun, Hang
Soroseris, Stebbinsia, and Syncalathium are three genera of the sunflower family (Asteraceae) with restricted distributions on high screes of the Tibetan Plateau. We present a molecular analysis to test the monophyly of the genera, evaluate the phylogenetic relationships and construct their biogeographic diversification history. Nuclear ITS and plastid trnL-F and psbA-trnH fragments were analyzed with parsimony, Bayesian inference, and relaxed Bayesian dating for all species of Soroseris, Stebbinsia, and Syncalathium. Stebbinsia is part of a polytomy with several lineages of Soroseris. Syncalathium is biphyletic with Syn. souliei placed within subtribe Lactucinae and the remaining species close to the Soroseris-Stebbinsia clade within subtribe Crepidinae. Bayesian dating based on ITS sequences and using four fossil calibrations suggests that the stem and crown ages of the Soroseris-Stebbinsia clade and the two groups of Syncalathium are between 8.44 and 1.56 million years. Stebbinsia should be treated as a section of Soroseris and Syncalathium souliei should be excluded from Syncalathium and either placed in Lactuca s.l. or established as a new genus in Lactucinae. The remaining species are to be treated as Syncalathium s.str. in Crepidinae. The diversification of these groups in the Tibetan Plateau is of relatively young age, and can be explained by rapid diversification and radiation of the Soroseris-Stebbinsia clade, allopatric speciation within Syncalathium s.str. and convergent evolution of Syncalathium s.str. and Syn. souliei. The speciation events correlated with climatic change and fragmentation of scree habitats during the uplift of the Tibetan Plateau. Possible migration routes in Syncalathium s.str. from the northeast to the central and southern part of the Tibetan Plateau are suggested.