不同尺度景观要素对短花针茅种群遗传多样性与遗传结构的影响

Integrating landscape factors to address species microevolution processes has being received more attention. This study was carried out in the region of Stipa breviflora grassland, which is distributed continuously along Inner Mongolia plateau, Ordos plateau and parts of Loess plateau. Field sites were selected according to the grid method, and individual samples of S. breviflora were collected in each site. Genetic information was acquired using SSR markers. Characteristics of genetic diversity, genetic structure, gene flow and genetic discontinuities of the population were analyzed by applying both traditional population genetics approaches and landscape genetics approaches. Finally, through incorporating spatial thematic dataset on different scales such as climate, topography and land use with genetic information by means of GIS and geostatistics tools, key environmental factors affecting genetic differentiation of the species were illustrated. This study could explore genetic characteristics of S. breviflora population systematically, and show impacts of natural and anthropogenic factors derived from different scales on genetic diversity and structure of the population. It was also helpful to clarify the scale effect, and then to demonstrate the mechanism of genetic differentiation of S. breviflora. The results were expected to enrich the study of landscape genetics, to understand the evolution of S. breviflora grassland and/or the east part of Eurasian steppe. The study also provided information for biodiversity conservation of Stipa grassland affected by both climate change and human activities in future.

整合景观要素探讨物种的微进化过程受到普遍关注。本项目以连续分布于内蒙古高原、鄂尔多斯高原与黄土高原（部分）的短花针茅草原为研究区域，依据规则（网格）取样的方法设置样地，采集短花针茅个体样本；利用SSR分子标记手段，获取短花针茅种群遗传信息；利用传统群体遗传学与景观遗传学等方法，分析短花针茅种群遗传多样性、遗传结构、基因流以及遗传不连续体等特征；最后，集成气候、地形地貌、土地利用等多尺度空间专题数据，利用GIS技术与地统计学等方法，探究影响短花针茅群体遗传分化的关键环境要素。通过上述较为系统的研究，阐明自然与人为因子对短花针茅遗传多样性与遗传结构的影响，明晰不同环境要素的尺度效应，从而揭示出短花针茅种群遗传分化的机制。其结果不仅丰富了景观遗传学内容，而且有助于深刻认识短花针茅草原（乃至欧亚草原东部）的演化，对于未来气候变化和人类活动共同作用下针茅草原的生物多样性保护也具有重要的参考价值。

自然与人类活动不断塑造着地球表面的景观格局，改变基因流，从而对生物多样性产生重要影响。因此，整合景观要素探讨物种的微进化过程受到普遍关注。本项目以短花针茅为对象，利用分子生物学的手段，分析了降水梯度、温度梯度、农牧交错带短花针茅遗传多样性与遗传分化，主要结果为：（1）基于对转录组数据的分析，获得21个EST-SSR引物以及9个表征放牧作用的SSR引物；（2）分布于内蒙古高原、鄂尔多斯高原与黄土高原的短花针茅群体具有较高的遗传多样性，遗传变异主要来自于群体内，群体间基因流较强，导致群体的遗传分化程度相对较低，遗传距离与地理距离没有表现出显著的相关性，但是与环境距离显著相关，即在东西样带上表现为与温度因子、降水因子显著相关，在南北样带上表现为与温度因子显著相关；（3）土地利用的改变，加剧了短花针茅生境的破碎化，加强了群体间的基因流，提高了遗传多样性，削弱了遗传分化。不过，大面积集中分布的农田，也同时成为了与远距离群体进行基因交流的阻力，导致发生温度主导的群体遗传分化。另一方面，放牧直接改变了短花针茅的基因序列，从而提高了遗传多样性，促进了群体遗传结构的分化；（4）在大的空间尺度下，短花针茅群体间的遗传分化较大，基因流较小。短花针茅群体存在谱系地理结构，其起源时间虽然较晚，但是种群扩散较快。上述结果揭示出影响短花针茅遗传多样性与遗传分化的驱动力，阐明了人类活动的影响与作用机制，深化了放牧对植物遗传多样性影响机制的认识，丰富了景观遗传学理论，对于开展针茅属植物的相关研究也具有重要的参考价值。到目前为止，本项目发表学术论文5篇，支持6名硕士研究生完成了学位论文，其成果多次在国内学术会议上进行口头与墙报交流。