对于北极-高山植物的起源模式有两个观点：1）起源于温带高山地区，在第三纪末期向北极扩散；2）北方地区起源，通过长距离传播或在冰期向南方高山发生迁移。两个观点都得到分子谱系地理学研究的支持，但研究对象多是陆生植物，对水生植物的研究很少。申请人选取北温带高山分布的水生植物杉叶藻及其近缘种进行研究，已完成研究发现中国地区存在两个分化谱系，谱系地理结构明显，且形成杂交带。但由于采样范围的限制，杉叶藻的起源-迁移模式及谱系分化原因等关键科学问题并未解决。本项目拟扩大采样范围，利用叶绿体片段、核微卫星标记和RAD 测序，通过系统发育重建、群体遗传学分析、BSSVS模型、ABC模型、适应性分析，揭示杉叶藻在世界范围的遗传多样性、谱系地理结构及种群历史动态，阐明其起源与扩散路线，解析谱系遗传分化的过程与机制，探讨第四纪气候可能的作用和影响，为北温带高山水生植物的起源与进化提供新的研究案例。

Two main hypotheses have been proposed to explain the origin of arctic-alpine plants: (1) south-to-north migration from temperate mountains during the late Tertiary (2) north-to-south migration during the Pleistocene or by long distance dispersal. Both hypotheses were supported by recent phylogeographic researches, but most of them were focused on terrestrial plants and seldom on aquatic species. In present study, we focus on a north temperate alpine aquatic herb Hippuris vulgaris, as well as its sister species. Our completed work revealed two divergent clades with phylogeographic pattern and narrow “hybrid zone” in China. But we couldn’t address the key questions of the origin and migration route and the process of intraspecific divergence with limited samples. Therefore, we plan to cover the range of H. vulgaris in the world, using cpDNA fragments and nuclear SSR markers and RAD-seq to reconstruct the phylogeny of Hippuris and analyze population genetics. We use BSSVS and ABC simulation to reveal the origin, migration route and demography history of H.vulgaris. Correlation of neutral and outlier loci in RAD data with geographic distance and climate varieties will be estimated to test the divergence pattern of vicariance or adaptation. At last, we discuss the possible effects of Quaternary climate oscillation on the evolution history of H. vulgaris，thus offering a new case study on the origin and evolution of north temperate alpine aquatic plants.