滇东南硬叶兜兰核心种质区群体遗传结构

本研究选取国内主要种质采集区-滇东南石灰岩地区7个不同干扰居群为研究对象，旨在对其居群内和居群间遗传变异进行比较研究，以期对其保护措施的提出提供理论依据。通过利用SRAP标记对167个体的遗传多样性和遗传结构研究，结果表明：10对SRAP引物共扩增出288个位点，多态位点比率（PPB）达81.25%，香侬指数（I）为0.3709，在种水平上的具有较高遗传多样性；而居群水平上的多态位点比率仅为47.92%, 香侬指数为0.2348, 居群间平均Nei’s遗传距离为0.1268。经分子遗传变异方差分析（AMOVA）表明，有66.27%的遗传变异来源于居群内，居群间变异占总变异33.73%，此结果与遗传分化系数（Gst=0.3568）结果吻合，居群间基因流（Nm）为0.902, 不同地区间硬叶兜兰居群存在较高的遗传分化; 7个居群的UPGMA聚类在遗传相似性系数达0.863，聚为两支；经Mantel检测（r =0.298, P＞0.05），表明居群间遗传距离与地理距离无显著相关性。居群当前较高的遗传分化与其交配系统有关，其次，外在因素：人为采集、生境破坏和片断化造成居群内遗传多样性的丧失，加剧居群间的遗传分化，再次，遗传漂变也是另一重要影响因素；此外，适应性进化亦可能加剧了居群间的遗传分化，而基因流对遗传分化的影响不大。

Genetic Structure of Paphiopedilum micranthum Populations from Core Distribution in Southeast Yunnan

Paphiopedium micranthum is rare and endangered orchid known as slipper orchid. Its survival had been so seriously threaten that it lead to a drastic decline in number and range of wild population because of commercial need and habitation destruction In order to assess its influence on genetic structure of P. micranthum and provide fundamental information for its protection, 167 samples from seven populations under the different disturb circumstance in the over collection region were drawn to detect its genetic diversity and structure within and among populations by Sequence-related amplified polymorphism (SRAP) technology. Molecular marker revealed that it had a high level of genetic diversity at species level (PPB=81.25%; I=0.3709) despite small population sizes, a quiet low level at population (PPB=47.92%; I=0.2348), a moderate mean genetic distance among population (D = 0.1268). Analysis of molecular variance (AMOVA) indicated that the contribution (66.27%) of variability came within population level, which was consistence with the coefficient of genetic differentiation among populations (Gst=0.3568) result. P. micranthum maintained significantly higher population differentiation compared to other outcrossing orchid species. The current studies suggest that selective collection, habitats destroyed and fragmented lead to loss of genetic diversity within populations and aggravated gene differentiation In addition, a gene drift was very important reason responsible for a high gene differentiation adaptation evolution may be another reason for genetic differentiation. Genetic flow may be not the main factor for differentiation.