乌头属牛扁亚属（毛茛科）的系统发育和生物地理学研究

Plant origin, divergence and dispersal are important processes relevant to plant evolutionary biology that are not well understood for many groups of plants. Phylogenetic inference methods coupled with biogeographic analyses can yield insights into the processes of speciation and species divergence. An excellent candidate to explore such processes and improve our understanding is that of Aconitum subgenus Lycoctonum (Ranunculaceae). The proposed research will characterize the evolutionary history of this important lineage of plants through the combination of classical and Next-Generation Squencing methods to address three main objectives. The first objective includes increased taxon sampling in the Northern Hemisphere in order to cover the main infrageneric groups and main geographic distribution areas of Lycoctonum. The second objective consists of primer selection for single or low copy nuclear gene based on whole Transcriptome sequencing (RNA-seq). The third objective involves inferring the phylogenetic history of Lycoctonum through combining data from multiple plastid DNA regions, as well as estimating divergence times for individual clades based on assumptions of a relaxed molecular clock. Using these methods and other novel methods recently created for biogeographic area analyses the proposed research will reconstruct ancestral areas and migration pathways of Lycoctonum. This comprehensive approach promises to provide valuable insights into the temporal and spatial dispersal history of the biota through the combination of phylogenetic and biogeograpic data, incorporated with an extensive dataset on morphological and cytological characters for these taxa. This will not only enhance our understanding about the causal factors of the distribution pattern of extant floras, but will also create an excellent model system for the study of plant origin, divergence, dispersal, as well as provide the necessary ecological and evolutionary context for future studies concerning genome evolution in Lycoctonum.

植物类群的起源、分化和散布是植物进化生物学研究中的重要问题，系统发育和生物地理学研究相结合可以很好的揭示物种形成过程和分化式样。本项目拟以乌头属牛扁亚属为例，深入研究其系统发育关系和生物地理学历史。本项目将在前期研究基础上，继续在全球范围内对本亚属类群进行广泛取样，通过转录组测序（RNA-seq）及生物信息学方法来获取足够的单拷贝或寡拷贝核基因引物，结合多个叶绿体片段序列构建系统树并推测种间关系；运用松散分子钟方法，估算系统树上各分支节点分化的时间。在此基础上，运用多种生物地理学分析方法，结合形态学、细胞学和地质资料，探讨牛扁亚属的生物地理学历史，重点推测该亚属的起源时间、起源地点及其在北半球的迁移路径，了解其现代地理分布格局的历史成因。本项目的开展将对植物进化，尤其是物种形成、分化和散布研究提供一个翔实的案例，也为今后深入研究牛扁亚属多倍体基因组进化奠定坚实的基础。

乌头属牛扁亚属Aconitum subgen. Lycoctonum 属于毛茛科翠雀族，全世界约 40 种， 分布于欧洲、亚洲 、非洲北部和北美东部。该亚属的系统发育关系和生物地理学历史还不明确。本项目选取牛扁亚属40种、4变种共61个样品(约包括该亚属87%的种类，涵盖所有组、系)，乌头亚属33种植物，通过对psbD-trnT、trnT-trnL、ndhF-trnL、ITS、ETS和AP3片段获取核苷酸序列，进行了系统发育和生物地理学分析。分子系统学研究结果表明目前的牛扁亚属不是一个单系，不应包括独花乌头和A. moschatum。该亚属可分为展喙乌头组和牛扁组，展喙乌头是整个亚属的基部 类群，牛扁组可进一步分为五个系。系统发育分析结果支持横断山区的多倍体有较为相近的亲缘关系，与形态学和细胞学的研究结果一致，花葶乌头很有可能是它们的祖先种。赣皖乌头是四倍体狭盔高乌头的亲本之一，结合形态特征和地理分布，我们推测狭盔高乌头在华东一带起源后，向中部扩散到目前的分布区域。受趋同进化影响，狭盔高乌头有些居群在形态特征上与高乌头相似，但后者是否参与狭盔高乌头的物种形成还不得而知。生物地理学分析表明，牛扁亚属大约起源于中新世中期（10.63 Ma），随后向西扩散到欧洲大陆，向东经白令海峡扩散到北美。分布于横断山区的多倍体起源于3个百万年左右，与横断山区的隆起与形成时间十分吻合，该地区特异的地理环境及生境在多倍体的物种形成中起到了十分重要的作用。我们对狭盔高乌头、赣皖乌头、高乌头和分布于北美的A. reclinatum进行了全叶绿体基因组测序，结合NCBI现有的乌头属叶绿体基因组数据，进一步证实了赣皖乌头为狭盔高乌头的母本。本研究首次对牛扁亚属进行了全面的系统发育和生物地理学分析，深入探讨了多倍体的物种形成和进化历史，为相关研究提供了一个翔实的案例。