核桃属姊妹种的谱系生物地理学和物种分化研究

新生代以来剧烈的地质和气候变化，特别是第四纪冰期和间冰期的反复交错对温带植物类群的地理分布格局、群体结构和物种分化造成了深刻影响。植物的群体进化历史研究可以揭示其适于或制约适应性进化的能力并有助于预测对未来环境变化的响应。核桃楸（Juglans mandshurica Maxim）和野核桃（Juglans cathayensis Dode）是核桃属分布在不同地理区域，但形态上较为相似的姊妹种。核桃楸主要分布在我国东北、华北地区，野核桃主要分布在秦岭以南的亚热带山地。我们拟利用叶绿体和核基因标记对核桃楸和野核桃，开展谱系生物地理学研究。通过形态数据和基因谱系分析，揭示两个姊妹种的群体结构和遗传分化，确认二者可能存在的杂交和基因流；同时结合生态位模型，推断其种群动态和群体建立过程以及第四纪冰期可能存在的避难所和扩散路线，从而探讨我国北方及亚热带山地地区温带落叶森林树种的群体历史和物种分化过程。

Geological events and dramatically global climate changes over the Cenozoic, in particular Quaternary climatic osillations, have had remarkable influences for most temperate flora in their distribution, population structure and speciation. Studies on the evolution of populations during historical fluctuations in climates can reveal the capacity for and constraints on adaptive evolution and may help supply predictions about evolutionary responses to future enviroments.Juglans mandshurica Maxim and Juglans cathayensis Dode are sister species that distributed in different habitats and are similar in morphology. Juglans mandshurica is distributed mainly in northeastern China and northern China, while Juglans cathayensis is distributed in subtropical China. In this project, we intend to address the questions of population structure, species differentiation, hybrid and gene flow between Juglans mandshurica and Juglans cathayensis based on chloroplast,and nuclear DNA markers by employing a phylogeography approach. We will also use ecological nich model to locate possible refugia and recolonization routes,and to detect process of population demography. The genetic and morphological data combined with ecological niche modelling will help us understand how temperate deciduous trees responded to previous periods of rapid climate and enviromental change in terms of speciation mechanism.