华北地区小丛红景天种群的AFLP遗传多样性

Population genetic diversity of Rhodiola dumulosa in Northern China inferred from AFLP makers

利用扩增片段长度多态性(AFLP)标记,对分布于华北地区5个山脉的25个小丛红景天(Rhodiola dumulosa)自然种群的776个样品进行了遗传多样性和遗传结构的研究。结果表明:华北地区小丛红景天种群具有较高的遗传多样性,4对选择扩增引物共扩增出398条清晰的条带,其中多态带312条,种群的平均多态位点百分率为78.46%,种群总的Nei's基因多样性为0.3649,总Shannon多态性信息指数为0.5422。华北地区小丛红景天种群间的遗传分化系数Gst=0.1507,基因流Nm=2.8179,表明种群间遗传分化较低,有一定的基因交流。AMOVA分析结果也表明:华北地区小丛红景天的遗传变异主要存在于种群内,地理单元间有一定的遗传分化,而种群间的遗传分化较低。STRUCTURE的分析和UPGMA聚类分析结果一致,结果显示地理分布距离相近的种群优先聚在一起。Mantel检验也进一步证实,华北地区小丛红景天种群的遗传距离与地理距离间呈显著的正相关关系(r=0.5129,p<0.001)。种群的遗传多样性与海拔呈显著的负相关关系(p<0.05),而与坡向没有显著相关性。用Dfdist软件分析海拔对遗传多样性的影响,结果表明没有显著的受选择位点。

Aims Rhodiola dumulosa （Crassulaceae） is a perennial herbaceous plant. It grows among rocks on mountains at 1 600–3 900 m,and its populations are spatially scattered in their areas of distribution. Our objectives were to study the population genetic diversity and genetic structure of R. dumulosa in northern China and determine relationships between genetic diversity and environmental factors. Methods We analyzed 776 individuals from 25 natural populations using amplified fragment length polymor-phism （AFLP） markers. Important findings We obtained 398 unambiguous bands from the four pairs of selective primers,312 bands （78.46%） of which were polymorphic across all individuals. The Nei＇s gene diversity was 0.364 9,and the Shan-non＇s information index was 0.542 2 at the species level. Therefore,there was a high level of genetic diversity within R. dumulosa populations in northern China. The population genetic differentiation index Gst was 0.150 7,and the indirect estimate of gene flow Nm was 2.82,which indicated that genetic differentiation among northern populations was low and gene exchange was frequent. Analysis of molecular variance （AMOVA） revealed that the majority of AFLP variations resided within populations （67.9%）. The STRUCTURE and UPGMA cluster analyses showed that the closely related populations are geographically restricted and occur in proximity to each other. This result was confirmed by the Mantel test,which revealed a significant positive correlation （r = 0.512 9,p 0.001） between geographical distance and genetic distance. In addition,the correlation analysis of population genetic diversity and altitude showed a significant negative relationship （p 0.05）,i.e.,population genetic diversity decreased with increasing altitude. However,there was no significant correlation between genetic diversity and slope direction. The software Dfdist was used to detect outliers caused by altitude,but the results were non-significant. All research results showed that geographical distance affected genetic distance significantly.