资源植物四倍体物种小大黄的进化历史研究

重要资源植物大黄属既有二倍体也有四倍体物种。申请者已有的分子证据表明四倍体物种小大黄同一基因位点克隆序列分别聚集在两个不同的进化分支上，可能是一个异源多倍体物种。但是该物种的起源和进化历史仍然不清楚，如：该物种什么时候发生的多倍化？它是大黄属两大分支现有二倍体物种共同祖先、通过杂交异源多倍化产生的，还是两支现有二倍体物种起源后再杂交产生的多倍化物种？本项目拟选择该小大黄多个代表性居群和两大支6个二倍体物种为研究对象，利用转录组学系统发育、基因组原位杂交、群体遗传学等证据，结合生态位模拟，全面探究该四倍体物种的基因组来源（父母本）、多倍化起源时间、母系起源次数以及物种对过去气候变化响应的群体扩张历史等科学问题。研究结果对于理解青藏高原高山植物的进化历史和多倍化物种形成机制具有重要启发意义，为有效利用这些资源植物提供基础。

Multiple radiations may together have leaded to the production of the current diploid and tetraploid resource species of the genus Rheum. The available molecular data suggested that the tetraploid Rheum pumilum might have arisen from allopolyploidization because the gene sequences from the same loci clustered into two different clades with other species. However, numerous key questions related to the evolutionary history of this species remained unclear, including polyploidization times and the diploid ancestors. In this study, we aimed to select representative populations of this species and six diploid species. We will use GISH and transcriptome phylogeny to determine its polyploidization time and construct phylogenetic relationships of the duplicated genes and orthologous genes from diploid species. We will collect population genetic data from chloroplast DNAs and nuclear loci and use phylogeographic and population genetic methods to analyze these datasets. We will combine all of these newly obtained data to clarify polyploidization time, ancestors, origin times and demographic response to the past climatic changes of this species. Our results will be highly useful for understanding speciation history of the polyploid species as an important resource plant.