兜兰属的系统发育与生物地理学研究

Southeast Asia harbors world's biodiversity hotspots, showing high species biodiversity and endemism. Although it occupies just 4% of the Earth's land areas, Southeast Asia is home to nearly one-quarter of all terrestrial species in the world, and over 50% of its land area is composed of islands and islands groups. On the other hand, owing to the successive expansion and contraction of distribution and the fragmentation of geographical barriers, the tropical flora greatly diversified in this region during a major part of Tertiary. Paphiopedilum, the largest genus of the subfamily Cypripedioideae (slipper orchids), is mainly distributed in Southeast Asia. The attractive flowers of slipper orchids make them have high ornamental and commercial values, and hold a special place in the hearts of botanists and hobbyists. However, the phylogeny, biogeographical history and mechanism of its species diversification are still largely unknown for this fascinating group. In this project, we aim to reconstruct the phylogeny of Paphiopedilum with multiple cpDNA and low-copy nuclear genes. In addition, we intend to explore the mechanisms underlying the development of the species diversity and distribution pattern of Paphiopedilum in Southeast Asia based on divergence time estimation, geographical distribution,paleoclimate, and geological evidence. This study would provide valuable insight into the evolution of Orchidaceae and the historical processes of plant species diversification in Southeast Asia.

东南亚为生物多样性研究热点区域，其陆地面积占全球陆地面积的4%，却拥有20-25%的物种多样性，且很多是特有种。该地区超过50%的陆地由岛屿和群岛组成。由于分布区连续的扩张、收缩和地理障碍的破碎化，该区域很多热带雨林植物区系在第三纪持续发生分化。兜兰属是杓兰亚科最大的一个属，主要分布在东南亚地区，花型奇特、花色艳丽，具有重要观赏和商业价值，深受植物学家及植物爱好者青睐。但该属的种间关系仍有待全面深入研究，其物种多样性的成因和现有分布格局的形成过程也很不清楚。本项目拟利用多个叶绿体DNA片段和低拷贝核基因，研究兜兰属的种间进化关系。结合分子钟估算、兜兰属地理分布和东南亚地区的古气候和地质特点等，探讨兜兰属物种多样性和分布格局的成因。该研究对揭示兰科和东南亚地区植物物种多样性的形成机制具有重要意义。

兜兰属是杓兰亚科最大的一个属，主要分布在东南亚地区。而该属的种间关系、物种多样性成因和现有分布格局的形成过程均有待深入的研究。本项目以兜兰属为研究对象，通过兜兰属物种的多基因序列构建了兜兰属的系统发育关系，结合网状进化分析、分子钟估算、古分布区重建和进化速率的分析探讨了兜兰属的物种分化。我们的研究结果如下：兜兰属存在复杂的网状进化事件；替代和长距离扩散对兜兰属现在的分布格局都起到了重要的作用；兜兰属存在进化速率的转换，进化速率的转换主要与兜兰亚属的多样性相关，且兜兰亚属进化速率的转换与晚新生代海平面的波动密切相关；网状进化和海平面的变化共同促进了兜兰属的物种分化。本研究对揭示兰科和东南亚地区植物物种多样性的形成机制具有重要意义。此外，我们将叶绿体片段和ITS的鉴定能力进行评估。我们的分析结果显示ITS是单个片段中鉴定成功率最高的，而matK + atpF-atpH是组合片段中鉴定成功率最高的，我们推荐将matK + atpF-atpH + ITS相结合用于兜兰属的物种鉴定。