喜马拉雅-横断山区高山植物钟花报春组（报春花科）的谱系地理学研究

The Himalaya-Hengduan Mountains is characterized by its particularly high biodiversity, which was considered as a natural laboratory for studying the mechanism of speciation. There are many differences in landscape, geological history, and impacts of Quaternary climate oscillations between the Himalaya range and the Hengduan Mountains, which are assumed to influence the evolutionary diversifications of plants in both areas. In this project, we will test the hypothesis by uncovering the phylogeographic pattern in an alpine plant group Primula sect. Sikkimensis (Primulaceae) in the Himalaya-Hengduan Mountains. This group consists of 8 species, but all endemic to this range. Primula sikkimensis is the only member of the section that is widespread from the Hengduan Mountains to the center range of Himalaya, while the others are narrowly distributed. We plan firstly to delineate these species’ boundary using DNA Barcoding and reconstruct their robust phylogeny. Secondly we will analyze their phylogeographic patterns using several chloroplast DNA loci and nuclear microsatellite markers (SSR). Many aspects of phylogeographic patterns, such as lineage divergence patterns and divergence times, demography histories, ancient areas and potential migration routines will be examined in this study. We will also use the Maximum entropy modeling to simulate their potential distribution ranges including the present time, the Last Glacial Maximum, and the Last Interglacial Period. At last, we will discuss the relationship among these phylogeographic patterns, geological histories, impacts of Quaternary climate oscillations, etc. The project will provide us both some basic knowledge for further uncovering the mechanism of recent radiation of the alpine genus Primula, and a typical case for studying the speciation of alpine plants in the Himalaya-Hengduan Mountains.

喜马拉雅-横断山区是研究生物多样性形成与维持机制的天然实验室。喜马拉雅和横断山区作为相邻的两个山地，在地貌、地质历史及第四纪冰期的影响方面都存在一定的差异，这对分布于这两个地区的植物有怎样的影响？本项目拟围绕该科学问题展开研究，计划选取喜马拉雅-横断山区特有高山植物报春花属钟花报春组为研究材料，用该组所有8个物种进行谱系地理学研究。本项目将首先采用DNA条形码和系统发育的方法确定物种界限和系统位置，再使用叶绿体片段和核基因SSR分析其谱系地理格局、群体动态历史、分化时间、祖先分布区及迁移路线等信息，并用生态位模型模拟该类群不同时期的潜在分布区；最后，本研究将结合该地区的地史及第四纪气候等资料，探讨钟花报春组物种演化方式及历史成因。本项目将为深入研究报春花属植物的辐射演化机制奠定基础，为研究喜马拉雅-横断山区特有高山植物的物种形成提供范例。

喜马拉雅和横断山区是生物多样性的热点地区，也是报春花属（Primula L.）的物种多样性中心。报春花属钟花报春组（Primula sect. Sikkimensis）约8种，集中分布于喜马拉雅和横断山区，是该地区高山类群的典型代表。本研究以钟花报春组为材料，开展以下研究：（1）钟花报春组的分子系统发育研究。研究有力证实了钟花报春组是单系群，网叶钟报春处于其基部位置；其他的钟花报春组物种的种间关系非常复杂，表明钟花报春组内的世系分化并不完全或存在广泛的杂交现象；钟花报春组的祖先分布于中喜马拉雅一带，之后迁移到达横断山区。（2）钟花报春组的谱系地理学研究。研究进一步证实了钟花报春组为单系。研究获得了8个主要单倍型群。中喜马拉雅的亚东和错那一带及西藏东南部的雅鲁藏布江大拐弯一带是钟花报春组单倍型分化最为多样和复杂的地区，而横断山区所有的钟花报春居群由一个单倍型群构成；研究表明横断山区的钟花报春组单倍型群约在一百万年以前由西藏东南部迁移而来，并在横断山区快速扩张，从而形成了横渡山区与西藏东南部和喜马拉雅地区明显分化。（3）钟花报春组微卫星引物开发研究。本研究首次利用磁珠富集法结合454高通量测序技术开发了钟花报春P. sikkimensis的微卫星引物，共扩增出17个有多态性的微卫星位点。大部分位点能在两个近缘种间跨种扩增。（4）钟花报春组的叶绿体基因组研究。本研究首次利用基因浅层测序法对4个钟花报春组物种的7个个体进行了测序，获得了这些物种的完整叶绿体基因组，并对其结构特征进行了详细描述。在与其他11个报春花属叶绿体基因组数据比较后发现，报春花属属下各物种的叶绿体基因组结构保守，种间差异较小。以上研究首次系统地探讨了钟花报春组内各物种的演化关系，有助于我们更好地理解喜马拉雅-横断山区快速分化植物类群的演化过程、为该地区生物多样性的形成和维持机制研究提供重要参考。