中国亚热带地区刺叶高山栎的群体进化历史与局地适应研究

Subtropical China is considered a key biodiversity hotspot in the world, but the response patterns of evergreen broad-leaved species inhabiting there to paleoenvironmental changes and the adaptive evolutionary mechanism driving and maintaining their lineage divergence remain poorly understand. Quercus spinosa is a long-lived tree species and represents a widespread component of laurophyllous taxon in this region which provides a perfect opportunity for studying adaptive evolution or local adaptation. Due to the limitation of the traditional molecular markers (i.e., cpDNA and nSSR) in previous study, we failed to rigorously elucidate the evolutionary demography of Quercus spinosa and the potential roles of environmental factors in shaping its current genetic structure across subtropical China. In the present study, we propose to utilize restriction-site associated DNA-sequencing (RADseq) technique combining a multidisciplinary approach (e.g., population genomics, landscape genomics and ecological niche models) to (i) illuminate its population structure, evolutionary demography, and gene flow pattern at different timescales, (ii) reveal the local adaptation process of Quercus spinosa during past climate change and elucidate the environmental forces for driving and maintaining its intraspecific lineage divergence, (iii) test the hypothesis how evergreen broad-leaved tree species in subtropical China responded to historical environmental change as well as predict the adaptive potential of this tree species under future climate change. These findings will not only contribute to a better understanding for the complex evolutionary history of evergreen broad-leaved tree species in this region but also provide new evidence for resolving the forming and maintaining mechanisms of their intraspecific lineages.

中国亚热带地区是生物多样性研究的热点区域，但该地区的常绿阔叶物种对古环境变化的响应模式及驱动和维持谱系分化的适应性进化机制目前仍不清楚。刺叶高山栎是我国亚热带地区的常绿阔叶森林树木物种，是研究生态和进化之间相互关系的理想模式材料。基于一代分子标记(如叶绿体DNA和核微卫星标记)，前期的谱系地理学研究未能充分解析其群体进化历史和驱动谱系分化的环境驱动力。本项目拟以简化基因组测序技术为研究手段，整合多学科(群体基因组学、景观基因组学等)的分析方法，解析刺叶高山栎的遗传结构，群体动态和基因流式样，追溯该物种的进化历史；揭示物种在环境变化时期产生的局地适应过程，阐明驱动和维持种内谱系分化的环境驱动力；检验亚热带地区植物响应气候变化的相关假说以及预测刺叶高山栎对未来气候变化的适应潜力。研究结果将为阐明该地区的常绿阔叶物种的群体历史和种下谱系的形成及维持机制提供新的证据。

本项目以简化基因组测序技术为研究手段，整合多学科(群体基因组学、景观基因组学等)的分析方法，解析刺叶高山栎的遗传结构，群体动态和基因流式样，追溯该物种的进化历史；揭示物种在环境变化时期产生的局地适应过程，阐明驱动和维持种内谱系分化的环境驱动力；检验亚热带地区植物响应气候变化的相关假说。主要获得如下结果：共获得130个个体的58,353个SNP位点解析刺叶高山栎的遗传分化、谱系地理结构及群体进化历史。聚类分析结果表明刺叶高山栎具有两个种下谱系，且这两个谱系之间具有相对独立的遗传组分。结合生态位模拟以及进化历史模型等多角度分析，我们推断上新世早期伴随的温度剧烈下降促使刺叶高山栎发生种内分化。此外，长期的地理隔离、生态因素变化以及自身生理特征维持了两个谱系之间存在高水平的遗传分化。第四纪冰期的气候动荡引发耐寒物种适生区的扩散，导致刺叶高山栎东西部谱系的二次接触。这些结果均支持中新世以来的地质和气候事件驱动和维持刺叶高山栎的种内分化及局地适应。研究结果将为阐明该地区的常绿阔叶物种的群体历史和种下谱系的形成及维持机制提供新的证据。