|摘要||乌拉特黄耆、边陲黄耆和Astragalus coluteocarpus Bioss.(为了方便起见，本文中将帕米尔黄耆拟定为该种的中文名称)是黄耆属中的三个形态上十分相似的近缘物种。为了明确它们之间的分子亲缘关系以及探讨分子证据能否支持边陲黄耆作为一个独立的物种，从分子水平上对它们进行了分析。此外，还选取这三个近缘物种作为研究对象来探讨古地质事件及气候变迁对西北干旱区山地植物空间遗传分布格局的影响。
本研究共收集这三个物种的23个居群的169个样本，其中乌拉特黄耆7个居群，共计69个样本；边陲黄耆12个居群，共计85个样本和帕米尔黄耆 4个居群，共计15个样本。根据筛选出的三个叶绿体基因片段（accD-psaI、trnC-rpoB和trnV）的变异位点，共得到15个单倍型，其中每个物种各存在5个单倍型，并且三个物种之间不存在共享的单倍型。单倍型的系统发育树及网络图显示每个物种基本都属于一个单独的分支。分子方差分析显示物种间有很高的遗传变异。中性检验和错配分析显示三个物种近期均没有经历居群的扩张过程。根据被子植物叶绿体DNA平均突变率得到种间分化时间在5.40-3.75 Mya (Million years ago)之间，种内的分化时间主要发生在2.34-0.21Mya之间。结果表明物种种子有限的扩散能力等可能导致了种间限制性基因流。种间的分化与第三纪青藏高原及其周边山系的隆升和持续增强的干旱化过程有关；而种内的遗传多样性与第四纪更新世冰期-间冰期循环有关。|
|其他摘要||Astragalus hoantchy Franch., A.dshimensis Gontsh. and A.coluteocarpus Bioss.(for convenience, pamier astragalus was served as a Chinese name of the species in this paper) are three related species morphologically. To explore their genetic relationship and A.dshimensis Gontsh.whether as a separate species or not, we conduct a molecular level study on these species. In addition, the three sister species of Astragalus L.were chose as model species to investigate the impacts of ancient geological and climatic events in northwest of China on the spatial genetic structure of mountains plants.
Two DNA sequences(a nDNA sequence ITS and a cpDNA sequence trnL-F) of 33 individuals of the three species were sequenced in this study. The intraspecific and interspecific genetic distances were calculated by Mega 6.06, the phylogenetic trees of Maximum Likelihood (ML) method and Bayes Inference (BI) were respectively reconstructed by Mega 6.06 and MrBayes3.2. The results shown that the intraspecific genetic distances of A.hoantchy Franch., A.dshimensis Gontsh. and A.coluteocarpus Bioss. were 0.000, 0.001 and 0.003 respectively, the average interspecific genetic distances between A.hoantchy Franch. and A.dshimensis Gontsh.was 0.010, that of both with A.coluteocarpus Bioss. were 0.015 and 0.016 respectively. Additionally, the average interspecific genetic distance between A.hoantchy Franch. and A.dshimensis Gontsh. was indicated to be larger than their intraspecific genetic distance. The phylogenetic trees used ML and BI method have a similar topological structure in which three distinct clades were comprised of individuals of three studied species respectively. This study not only revealed the genetic relationship of the three related species but also provided the molecular evidences that support A.dshimensis Gontsh.as a separate species.
We collected 169 individuals belonging to 23 populations of the three sisiter species, including 7 populations and 69 individuals of A.hoantchy Franch., 12 populations and 85 individuals of A.dshimensis Gontsh. and 4 populations and 15 individuals of Astragalus coluteocarpus Bioss.. According to screened three chloroplast regions accd-psaI, trnC-rpoB and trnV there were identifed 15 haplotypes, including 5 haplotypes in each species. No haplotypes have been shared between species. Haplotypes network and phylogenetic tree suggested that they clustered into three divergent lineages which mostly correspond to the three species. AMOVA (Analysis of Molecular Variance) showed the high levels of genetic differentiation occured at interspecific. Neutral tests and mismatch distribution analysis support no species had experienced demographic expansions recently. Based on the average substitution rate of cpDNA in Angiosperms, the genetic divergence time of interspecific were calculated at 5.4-3.75Mya(Million years ago) , while the intraspecific divergence mainly happened at 2.34-0.21Mya.Our results demonstrated that the high restrict gene flow at interspecific were because of the limit dispersal ability of seeds. The species-level divergence was most likely triggered by rapid uplift of Tibet Plateau and its adjacent mountains and the continuously enhanced aridification in Central Asia, while development of genetic variation at the intraspecific level might be attributed to climatic cycles in the Quaternary|
张杰. 黄耆属三个近缘物种的分子系统学和谱系地理学研究[D]. 北京. 中国科学院大学,2016.