菊科风毛菊属的系统学研究

Saussurea is a large north temperate genus of family Asteraceae. With about 70% its total species are found in China, genus Saussurea is most representative at subgenus and section level in this country. This group of plants plays an important significance for the ecological environment of alpine and arid regions. “Snow lotus”, which comes from some species of genus Saussurea, is popularly used in traditional medicine and highly sought after by tourists as a symbol of the alpine region, and thus some species are critically endangered. However, many Saussurea species are usually mixed together and very confusing in the “snow lotus” market. This kind of phenomenon causes great hidden trouble in medicine safety. Molecular phylogeny studies have shown that there is serious convergent evolution and parallel evolution phenomenon of some usually “important” taxonomic characters of genus Saussurea, and most of the subgenera and sections are paraphyletic groups. The present situation that the systematic research has fallen behind has restricted our understanding of the evolution of morphological characters in genus Saussurea and further to establish a reasonable classification system. In this study, we try to make comprehensive sampling of genus Saussurea, giving full consideration to the representation of both geographical distribution and biodiversity. The phylogenetic tree constructed based on about 10 DNA segments (including nuclear DNA and chloroplast DNA) will be used to resolve the phylogeny in the genus Saussurea. The further phylogenetic analysis will be conducted to elaborate the biogeographical history and the evolution of morphological characters within the genus. Based on molecular phylogeny and morphological analysis, a reasonable nature classification system of genus Saussurea is hoped to be established. This project will lay the foundation for further study on the classification and revision, speciation and adaptive mechanism of the genus, and will also provide a reliable reference for the ecological protection and the development and utilization of the plant resources in the alpine and arid regions.

风毛菊属为菊科的特大属，我国有约70%的种类，在亚属和组水平上极具代表性。该属植物对于维持高寒区和干旱区的生态具有重要意义，不少种类还是著名药用植物“雪莲花”的来源植物。初步的分子系统学研究结果显示该属的重要形态分类学性状存在严重的趋同演化和平行演化现象，根据形态性状建立的该属属下类群（亚属、组等）基本不是单系。迄今，我们对风毛菊属性状演化规律的理解还非常不全面，仍然缺乏一个合理的分类系统。本研究将在对风毛菊属植物全面取样的基础上，选取核基因和叶绿体基因共约十个基因序列区段开展系统发育研究，结合形态性状的分析，探讨该属形态性状演化的规律，在此基础上建立一个合理的属下分类系统，并重建风毛菊属的祖先分布区，探讨风毛菊属的起源、散布和进化历史。本项目将为风毛菊属进一步深入的分类修订、物种形成和适应性机制研究奠定基础，也将为高寒区和干旱区的生态保护、以及该属植物资源的开发利用提供可靠的参考依据。

风毛菊属是菊科菜蓟族的一个大属，约460种。该属在北半球广泛分布，青藏高原及其邻近区域为其分布中心。到目前为止还没有能够得到一棵高支持率的分子系统树。本课题对风毛菊属物种进行世界范围的代表性取样，使用叶绿体基因组数据和核基因组数据建立支可靠的的系统发育树，进而结合形态学、细胞学等证据探究风毛菊属的属下分类。然后依据所得到的系统发育树，进行生物地理学研究，探讨风毛菊属的起源、扩散与迁移。.1..风毛菊属属下系统重建.综合形态学、细胞学、分子系统学等证据，本研究保持原有系统四个亚属的划分，但是对其各个亚属内部的类群进行了调整。在对部分物种进行重新归类之后，形成了新的风毛菊属属下分类系统。形态学特征包括基生叶、花序、总苞片等形态性状以及染色体基数支持本研究所得的属下分类系统。.2.风毛菊属的起源与扩散.基于叶绿体基因组数据的估算结果显示风毛菊属大概起源于中新世早期。祖先分布区重建的结果显示，风毛菊属很在中新世于今天的亚洲温带干旱草原带开始分化，除原地扩散外，还分别向南部高海拔地区和北部高维度地区迁移。. 基于对气候变化和地质变化的分析，本研究认为风毛菊属的出现可能主要受三方面因素影响：(1)喜马拉雅及其邻近区域的隆起形成屏障，阻隔了风毛菊属祖先与其近缘类群的基因交流；（2）季风气候形成使得环境改变，为风毛菊属祖先的出现创造了条件；（3）中新世早期的温度适宜期，则为风毛菊属祖先类群的存活提供了保障。风毛菊属的扩散也可能主要受到三方面因素的影响：（1）中新世全球温度先上升再回落，为风毛菊属祖先向外扩散提供了条件；（2）天山地区的快速隆起，形成了一道天然屏障，阻碍了风毛菊属向西和向北的直接扩散；（3）喜马拉雅地区的快速隆起，除了阻碍其向西和向南的扩散之外，还在横断山区及其附近区域形成了大量新的环境，极大地促进了风毛菊属的快速分化，形成今天的分布中心。