景天科红景天属辐射性演化及其机制研究

Evolutionary radiation is generally recognized as an evolutionary event whereby many new phenotypic divergent species may arise from a common ancestor in a short geological time. This bursts of speciation, which is very common in plants, may occur in different periods of geological history, different areas, and lineages during evolution of plants. However, most studies of evolutionary radiations were descriptive, rarely on their mechanisms. It has been documented that evolutionary radiation occurred generally in response to the great changes in geology and environments. Thus, high species diversity could be expected in the region with high habitat heterogeneity and ecological niche differentiation. Meanwhile, evolutionary radiation could occur more commonly in taxon occurred in these regions. Recent studies showed that the Qinghai-Tibetan Plateau (QTP) triggered evolutionary radiation of some genera distributed in this area. Rhodiola is such a genus with species diversity center in the QTP. In this project, we focus on the pattern of species diversity in Rhodiola, and the processes and mechanism underlying the pattern of evolutionary radiation. In order to unravel the process and mechanisms responsible for the evolutionary radiation, the followings will be conducted in this study: 1) reconstructing a more powerful phylogeny of Rhodiola for dating different lineages of this genus and examining relationships between species and their habitats; 2) analyzing pattern of phenotypic evolution for adaptive radiations; 3) carrying on phylogeographic studies on three pairs of closely related lineages for the insight into the speciation during evolutionary radiation; 4) comprehensive analysis of findings in this study with the data from climatology and geology.

生物的辐射性演化是指在较短地史时间内源于同一谱系或祖先的生物种类急剧增加并在表型上出现明显分化的现象。辐射性演化在植物中十分普遍，体现在植物演化过程中的不同地质历史时期、不同地理区域以及不同演化阶段的植物类群中。目前对生物辐射性演化的研究多停留在描述阶段，有关其机制的报道较少。有证据表明，地质变化和环境变迁会引发和加剧物种的快速分化，致使特定地域或特定类群产生了很高的物种多样性。近期的研究表明，青藏高原的隆升催生了一些类群的快速演化，红景天属就是其中之一。本项目选择以青藏高原及其邻近地区为物种多样性中心的红景天属为研究对象，通过①多基因的系统发育重建，②形态和繁殖生物学性状的变异式样分析，③近缘类群的比较谱系地理学及生态位模拟分析，④综合分析上述研究结果并结合气候、地史等其它学科资料，探讨红景天属辐射性演化的过程和机制。

生物的辐射性演化是指在较短地史时间内源于同一谱系或祖先的生物种类急剧增加并在表型上出现明显分化的现象。阐明植物辐射性演化的原因和机制对于深入理解植物多样性的产生、维持、保护和利用具有十分重要的意义。本项目“景天科红景天属辐射性演化及其机制研究”以青藏高原及其邻近地区为物种多样性中心的红景天属（Rhodiola L.）为研究对象，通过对该属植物系统发育的重建、生物学性状变异式样的分析以及属内近缘物种的比较谱系地理学及生态位模拟分析，探讨红景天属辐射性演化的过程和机制。研究结果显示：1）红景天属的起源和快速演化的时间分别与青藏高原两次剧烈隆升的时间一致，这表明青藏高原的隆升促进了该属植物的快速分化和物种形成；2）青藏高原及其邻近地区拥有大量的特有物种，也是该属的物种多样性中心，这说明空间隔离和多样的生境促进了该属植物的物种形成；3）属内近期分化形成的类群，其形态变异往往较大，这显示该属植物尚处于快速分化之中；4）谱系地理学的研究表明，形态、地理与遗传变异式样受地形结构与气候变化的共同影响，但不同类群对于气候变化的响应具有类群特异性，进而导致不同类群具有不同的地理分布格局。