短花针茅谱系地理与遗传多样性格局形成机制

The union of phylogeography and landscape genetics, pushed forward by recent advances in theory, models, and methods, is ripe for investigating impacts of geographic and environmental factors on population dynamics, selection and adaptation, and gene flows in different spatial-temporal scales. Furthermore, it has allowed researchers to gain insights into biodiversity patterns and process, and to reveal mechanisms. This study was carried out in the region of Stipa breviflora distributed mainly in China. Field sites were determined according to its spatial distribution, and individual samples of S. breviflora were collected. The main studies included, (1) phylogeographic structure of S. breviflora was illustrated by use of cpDNA analysis. Intraspecific lineage divergence and its relationship with historical environmental changes were examined. (2) Characteristics of genetic diversity, genetic structure, and gene flows of S. breviflora populations were analyzed by applying SSR markers. Genetic differentiation among different spatial scales was explored. (3) The consequences resulted from changes in geography and environments, varying across space and time, on population differentiation were studied. And finally, the mechanism of genetic diversity pattern formation of S. breviflora was explained. This study could address basic questions relevance to phylogeography of S. breviflora, which is helpful to understand the origin and evolution of grassland in China. Moreover, this study could enrich knowledge in field of landscape genetics about S. breviflora. Therefore, it could be served as a case study on integrating phylogeography and landscape genetics.

现代分子生物学手段推动了谱系地理学与景观遗传学的联合，为阐明不同时空尺度下地理与环境要素对于群体历史动态、选择适应与基因流的影响，揭示生物多样性格局与过程及其维持机制提供了机遇。本项目以主要分布于我国的短花针茅为研究对象，针对其空间分布特点设计取样方案，并主要开展以下研究：（1）利用cpDNA技术，刻画我国短花针茅谱系地理结构，探讨其谱系分化及其与历史环境演变的关系；（2）利用SSR标记技术，分析短花针茅群体的遗传多样性、遗传结构、基因流等，探讨不同空间尺度下其群体的遗传分化特征；（3）利用RAD-seq等技术，研究地理与环境要素对短花针茅群体分化的影响，探讨短花针茅遗传多样性格局的形成机制。本项研究能够解决我国短花针茅谱系地理的基本科学问题，有助于深刻认识我国草原的发生与演化进程；同时，也丰富了对短花针茅景观遗传学的认知，为谱系地理学与景观遗传学的整合研究提供了案例。

谱系地理学与景观遗传学的联合，为阐明不同时空尺度下地理与环境要素对于群体历史动态、生态适应的影响，揭示生物多样性格局及其形成机制提供了机遇。本项目以主要分布于我国的短花针茅为研究对象，开展了短花针茅谱系地理学、群体遗传分化空间分布格局及其驱动机制等方面的研究。我们发现：（1）短花针茅起源于晚中新世（7.66Ma）的青藏高原东北部和贺兰山，从青藏高原东北部经祁连山南麓扩散到新疆，以及从青藏高原东北部与贺兰山扩散到蒙古高原、青藏高原西南部和河西走廊，扩张时间为1.5Ma左右，青藏高原的不断隆升、亚洲季风气候的加强促进了短花针茅的扩张以及各单倍型的演化；（2）短花针茅的遗传多样性处于中等偏低水平，其空间分布呈现出由分布中心向边缘地区递减的变化趋势，符合“中心—边缘假说”；（3）在区域尺度上，短花针茅群体可以分为东部、中部和西部3个亚群，东部和中部亚群的基因交流频繁。地理隔离是造成大尺度遗传分化的主要原因，昆仑山、天山和塔克拉玛干沙漠成为短花针茅群体基因交流的地理障碍；（4）短花针茅群体的遗传分化与驱动因素具有空间尺度依赖性，区域尺度群体比东西样带、南北样带群体具有更高的遗传分化水平，温度和水分因子在不同空间尺度上分别发挥着主导作用，适应高温、干旱、紫外线等非生物胁迫成为短花针茅群体产生遗传分化的主要机制。可见，本项研究刻画了短花针茅谱系地理结构，阐明了谱系与群体分化的历史过程，明晰了当代短花针茅群体遗传多样性与遗传结构，解析了地理以及环境要素对短花针茅群体谱系与遗传分化格局的影响，初步揭示出驱动的分子机制。研究成果丰富了针茅属植物谱系地理学与景观基因组学理论与实践，深化了对欧亚草原演化的认知。本项研究已发表学术论文3篇，其中，SCI收录2篇，CSCD收录1篇，拟发表SCI收录论文1篇。培养毕业博士研究生1名、在读博士研究生（拟2023年毕业）1名，培养毕业硕士研究生3名。

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