东亚特有间断分布类群双六道木属种水平谱系地理学和整合分类学研究

Diabelia (Caprifoliaceae) is an Asian endemic genus with a Sino-Japanese disjunct distribution pattern. It is likely possible to develop ornamental horticultural functions in this genus, because its flower color and form are diverse. Furthermore, some taxa within this genus have a high value for protection, because some of them are listed as endangered plants in China or Japan. However, due to possible inter-specific hybridization, inter-specific differentiation and/or recent convergent evolution, the species delimitation within the genus is disputed; moreover, the phylogeny within the genus and its speciation processes are not clear. This project will involve a collection of morphological characters and extensive sampling of the genus at the population levels throughout its known distribution. 1), we will use Restriction-site associated DNA sequencing (RAD-Seq), and Expressed Sequence Tags-Simple Sequence Repeats (EST-SSR) to analyze the population diversity and population genetic structure. 2), we will use phylogenetics and biogeography to infer the phylogeny, divergent time and biogeography events within Diabelia. 3), we will reveal the speciation process in Diabelia based on Ecological Niche Modeling (ENM) and Approximate Bayesian Computation (ABC) as well as by incorporating evidence we will obtain from our entire study. 4), we will utilize DNA barcoding techniques (ITS, trnL-rpl32, trnH-psbA, trnL-F, and matK), morphological character (including leaf size, corolla size etc.) statistics (e.g. Principal Component Analysis) and geographic distribution to precisely delimitate the species (or varieties) within Diabelia. Primarily, the project will provide theoretical evidence for the protection and ornamental horticultural development of species in Diabelia. In addition, the work can be a case study for Sino-Japanese disjunct flora research.

忍冬科双六道木属植物为典型的中国-日本植物区系类群，该属植物具有潜在的园艺观赏价值，部分类群被列为濒危保护植物。但迄今为止，由于可能存在种间杂交、近期种间分化和趋同进化现象，属内物种界定尚存争议、种间亲缘关系和物种形成过程不明确。本项目拟在该属分布区内系统地调查其性状并进行群体水平采样，1，运用限制性酶切位点关联DNA测序（RAD-Seq）和EST-SSR等分子遗传信息，阐明双六道木属种水平的遗传多样性和谱系地理结构。2，利用分子钟等推测种间的分化时间和进行祖先分布区重建，揭示该属种或谱系的群体进化历史。3，基于整合数据，结合生态位模型方法（ENM）和近似贝氏计算（ABC），揭示双六道木属物种形成过程。4，集成进化历史等研究结果，准确界定双六道木属疑难类群，提出该属整合分类系统。该项目将为双六道木属濒危植物的保护和开发提供理论依据，为中国-日本植物亚区植物的起源和演化提供案例。

双六道木属植物（Diabelia Landrein）隶属忍冬科北极花亚科，为典型的中-日-韩间断分布类群。由于属内存在种间杂交、近期种间分化和趋同进化现象，加之前期研究取样较少、使用的分子片段较少，双六道木属属下系统发育关系和生物地理研究尚不明确，属内物种的界定尚存在争议。本研究基于双六道木属植物分布区内66个居群的549个个体植物样品，应用ANOVA 和线性回归等形态统计、叶绿体片段测序、核基因微卫星位点扩增、浅层全基因组测序和生态位模型模拟等方法对双六道木属进行了系统发育和生物地理学等研究。居群遗传多样性与谱系地理结构显示双六道木具有37个cpDNA单倍型，单倍型网络分析显示该属具有典型的多起源分布结构和漫长的进化历史。双六道木属较高居群间遗传分化与总遗传多样性以及较低的平均居群遗传多样性，且地理距离与遗传距离之间存在显著相关性。双六道木属叶绿体基因组长度范围为156,243到157,578 bp之间，其中大单拷贝区89,539–90,801 bp，具有81个编码基因区域和130个非编码基因区域，8个高变异基因间隔区。双六道木的冠群时间点为28.31 Ma [95% HPD: 22.73–32.95 Ma]，四个物种全部在第三纪就已完成物种分化，较早分化的中国地区居群为原始遗留居群。双六道木属植物于第三纪渐新世时期开始分化，中国D. ionostachya居群为原始遗留居群，日本地区居群在近期没有经历过大范围的瓶颈作用，居群相对稳定居群，群体遗传多样性低，居群之间遗传分化高等特点。在双六道木的种群进化历史上，基因流动中断和遗传漂变是影响日本现有种群结构的主要因素。现有分子数据支持双六道木属属下四个物种，即D. serrata, D. spathulata, D. sanguinea 和D. ionostachya的分类学处理。