花柱二型性水生植物莕菜的适应性遗传进化研究

Aquatic plants is a special group with widely distributed regions, contrasting habitat conditions and striking reproductive systems comparing with terrestrial plants. Populations living in heterogeneous habitas are likely to ungergo diverse selective constrains than can differentially shape genetic variation. In order to learn the generation of genetic differentiation, it is necessary to identify loci potentially under selection. Climate and environment are key factors determing the distribution and evolution of aquatic plant species, Nymphoides peltata selected as material to study how these factors exert selective pressure on loci. N. peltata is distylous clonal perennial aquatic macrophyte with attractive sexual system widely distributed in China. Some loci detected in N. peltata genom whose level of differentiation between populations exceeds that expected under neutral expectations, the mechanism of loci correlated to selective factors is unclear. We plan to use amplified fragment length polymorphism molecular markers to study adaptive genetic differentiation of N. peltata from contrasting habitat. Identify and analysis these loci potentially under selection considering the correlation of climate and environmental factors to learn directional selection mechanism. Comprehensively reveal the adaptive genetic differentiation pattern and provide information to understand adaptive evolution of aquatic plant species.

水生植物是一个特殊类群，分布广泛，生境条件多样，繁殖方式特殊，与陆生植物有明显差别。生活在异质环境下的水生植物居群经受不同的选择，会形成它们遗传分化上的差异，要了解其分化产生的原因，对这些受选择位点的筛选和分析十分重要。气候环境因素对水生植物的分布和进化有重要影响，为探讨气候环境如何对水生植物的适应性进化起作用，我们选用了莕菜作为研究材料，莕菜在我国分布广泛，性系统特别，为花柱二型性多年生水生浮叶植物。前期研究发现莕菜某些位点分化异常可能遭受选择，但促进这些位点分化的机制不清楚。本项目拟采用AFLP分子标记，对分布于中国的莕菜居群进行适应性遗传分化研究，筛选出受选择位点并与气候环境因子进行相关性分析，阐明气候环境因子对这些位点定向选择的作用机制，从而全面揭示莕菜适应性分化模式，为理解自然界中水生植物的适应性遗传分化提供资料。

水生植物居群生活在异质环境下将经受不同的选择，会使它们的遗传分化产生差异，要了解分化产生的原因，需要对受选择的位点进行筛选和分析。本研究利用AFLP和SSR两种分子标记对中国51个莕菜居群进行了研究结果如下：基于SSR的PCO分析，居群分布较分散，而基于AFLP的PCO分析，居群分布较紧密，根据Nei’s遗传距离对居群构建的无根邻接树显示了同样的结果,显示两种标记产生了差异。基于SSR的AMOVA分析显示居群内变异率26%居群间变异率74%，而基于AFLP的AMOVA分析显示居群内和居群间的变异率均为50%。基于AFLP和SSR的Mantel检验都显示地理距离和遗传距离没有显著相关性。利用BayeScan软件对由AFLP得到的271个位点受自然选择的概率进行分析，得到有111个位点受筛选的概率很肯定，表明这些位点明显受到了自然选择作用而分化异常。这些环境相关的分子标记多态性被认为是适应性遗传差异的证据。目前此方面研究多集中在陆生植物，而水生植物鲜有研究。本项目筛选到了分化异常的位点，为研究水生植物适应性进化提供了思路。