中国特有橿子栎组（栎属）物种形成和生态适应机制研究

Understanding the genetic relationships, evolutionary history and processes of adaptive evolution among closely related species undergoing adaptive radiation is a major goal in evolutionary biology and a prerequisite of biodiversity formation. This project will use three closely related oak species from the Chinese endemic section Echinolepides of genus Quercus, which mainly distribute across the Qinling Mountains, as a model case to estimate the genetic compositions of these closely related species at the genomic level based on population genomics with restriction-site associated DNA sequencing (RAD-seq). The patterns of genetic differentiation and genetic relationships, as well as the characteristics of interspecific gene flow and complex evolutionary models among the three oak species will be investigated to evaluate the species convergence using coalescent-based analyses. Additionally, in order to explain the impacts of past geological and climatic changes on genetic differentiation and phylogeny of the three closely related oak species from Quercus section Echinolepides, methods of biogeography and landscape ecology will be integrated to reconstruct the evolutionary history and lineage diversification of the three oak species; the correlations between heterogeneous environments of Qinling Mountains and varying patterns of adaptive evolution among the three oak species will be investigated to explore the abiotic triggers for species differentiation. Our results will illustrate the genetic background and genetic relationships of the three closely related oak species from the endemic section Echinolepides at the genomic level, and demonstrate the patterns of lineage diversification and adaptive evolution of these oak species. Furthermore, this research will provide critical information to get a better understanding of the speciation, lineage diversification and adaptive evolution of forest tree species in Qinling Mountains, and give an important example for resource protection of endemic tree species in China.

经历辐射分化近缘物种的遗传关系、物种演化历史和适应性进化特征是进化生物学研究的焦点，也是理解生物多样性形成的前提。本项目拟以秦岭地区集中分布的中国特有橿子栎组三个近缘物种为研究对象，采用基于简化基因组测序的群体基因组学方法研究该组近缘物种基因组水平的遗传组成，揭示近缘物种遗传分化格局和遗传关系，基于溯祖理论等方法构建近缘物种之间基因交流式样和复杂系统演化特征，探讨近缘物种收敛性。结合生物地理学和景观生态学方法重建橿子栎组近缘物种的进化历史和时空演化动态，研究物种分化的外界驱动力，揭示过去地质、气候变迁事件对该组近缘物种遗传分化的塑造作用，探讨秦岭地区异质性环境与物种适应性进化的关联。本项目结果将从基因组水平反映中国特有橿子栎组三个近缘物种的遗传背景和亲缘关系，揭示该组物种的系统演化历史和适应性进化特征，为研究秦岭地区森林树种的起源、演化和适应机制，以及我国特有树种的资源保护提供参考依据。

栎属（壳斗科）物种丰富，构成北半球森林生态系统的重要建群树种。栎属近缘物种的分化受表型可塑性、种间基因渐渗和进化历史影响呈现复杂的模式，揭示栎属近缘物种分化式样和演化动态对研究植物物种形成和世系演化有重要的意义。本项目整合叶表型特征、多类型种群遗传学数据和景观遗传分析研究了秦岭地区集中分布的中国特有橿子栎组三个近缘物种（橿子栎、匙叶栎和尖叶栎）的种间分化特征，重建了三个近缘物种世系演化模型，进一步探讨了该组近缘物种适应进化的可能驱动因素。项目研究结果显示橿子栎组三个近缘物种具有显著的种间表型差别和遗传分化特征，近缘物种对集中分布区域内生物气候因子表现出明显的适应差异。橿子栎组三个近缘物种可能于渐新世中期至中新世早期发生辐射分化，并在长期演化过程中固定差异的物种基因库，产生完整的生殖隔离。秦岭及周边山区异质性气候因素变动可能是橿子栎组三个近缘物种世系分化的主要驱动力，同时也塑造了物种复杂的种群遗传结构和生物地理格局。本项目为栎属旧世界栎分支物种演化提供新的研究案例，有助于理解栎属物种差异世系多样化的驱动和维持机制。