丽江云杉和青扦的种间基因流波动

The changes of species' range are always accompanied with the changes of effective population size for forest tree species, which further trigger the fluctuant gene flow between related species. Picea likiangensis and P. wilsonii are important forest resources species with wide distribution in China; especially, these two species have been widely overlapped in distribution on the eastern Qinghai-Tibet Plateau. In this project, we will collect a large number of samples through hard field work, and present a high-resolution DNA sequence-dataset from multiple independent loci across the nuclear genome of these two species. We will determine the genetic limits between P. likiangensis and P. wilsonii, and examine the changes of species' range and interspecific gene flow using the likelihood or Bayesian computational tools based on coalescent theory and approximate Bayesian computation. Further, we will discuss the influence to the demography of P. likiangensis and P. wilsonii by the glacial and interglacial cycles during the Quaternary period. These results will extend our understanding of how the distribution of forest species and the formation of spruce species respond to the historical climatic changes. Moreover, all these results will provide important theoretical basis for conservation of spruce wild genetic resources in china.

林木物种中有效种群大小的变化常伴有物种分布范围的变化；进而，这些变化 可能引起近缘物种间的基因流波动。丽江云杉和青扦是在我国广泛分布的重要林木资源物 种，在青藏高原东部有大面积重叠分布。在本项目中，我们拟通过高密度取样，研究两个物 种核基因组上多个独立基因座的DNA序列群体遗传变异数据；利用基于溯祖理论的似然或贝 叶斯计算工具以及近似贝叶斯模拟工具，界定这两个物种，检测两个物种起源以后分布范围 以及种间基因流的变化；进一步深入理解第四纪冰期和间冰期气候变化对丽江云杉和青扦分 布变化以及种间基因流的影响。这些研究结果将增进我们对气候变化历史与林木物种分布、 物种形成等机制的理解，进一步还将为保护中国的林木野生遗传资源提供理论依据。

树木物种的分布和形成是林学研究的重点内容。本课题以丽江云杉和青扦两个广布树种为材料，基于5954条序列、134个样地信息和多种技术手段，揭示丽江云杉和青扦的分布变化，并探讨物种分化过程中可能出现的基因流波动。结果表明，丽江云杉和青扦具有不同的遗传结构和分布范围，支持其物种分类地位；其种群大小、分布范围和种间基因流强度都发生过明显改变。特别是在末次冰期后，两个物种重叠分布区面积增大，使得两个物种有更多机会杂交并发生基因交流，种群分化水平降低。本研究表明，受到气候变化影响，物种分化时的种间基因流可呈现波动变化式样。