中国特有濒危树种毛红椿核心和边缘居群的遗传多样性

选用8对多态的微卫星引物, 研究了毛红椿(Toona ciliata var. pubescens)核心居群和边缘居群的遗传多样性。研究结果显示, 边缘居群的观察等位基因数和有效等位基因数并不比核心居群低, 甚至更高。普通广布和稀有地方等位基因在所有居群中均有分布, 而普通地方和稀有广布等位基因分别仅在5个和3个居群中有分布。从4种类型等位基因总数上看, 边缘居群高于核心居群, 特别是边缘居群的稀有地方等位基因数量明显多于核心居群。边缘居群的平均期望杂合度和观察杂合度都高于核心居群。核心居群间的基因分化系数为0.1520, 边缘居群间为0.3045, 边缘居群与核心居群的遗传分化差异达到显著水平。核心居群间基因流大于1, 而边缘居群间基因流小于1, 说明核心居群间基因交流频繁, 边缘居群由于片段化和地形影响, 基因流较小。Mantel检验结果显示, 居群间遗传距离与地理距离的相关性不显著, 说明地理距离对毛红椿居群遗传分化的影响不显著。

Genetic diversity of central and peripheral populations of Toona ciliata var. pubescens, an endangered tree species endemic to China

Aims Our objective was to elucidate the genetic diversity of central and peripheral populations of Toona ciliata var. pubescens and whether there existed “central-peripheral hypothesis” in these populations.
Methods We analyzed 384 individuals from nine natural populations using eight pairs of polymorphic SSR primers.
Important findings The mean number of observed and expected number of alleles in peripheral populations were not lower, but higher than those in central populations. Common widespread and rare local alleles were distributed in all populations, but common local and rare widespread alleles were found in five and three populations, respectively. Both the observed and expected heterozygosities were higher compared to the central populations. The coefficient of gene differentiation of the peripheral populations was 0.304 5, which was significantly higher than that of the central populations (F_ST = 0.152). The gene flow between central populations was greater than one, but less than one between peripheral populations. These indicated that frequent gene flow existed between central populations, while terrain and fragmentation prevented gene flow among peripheral populations. Mantel test indicated no relationship was found between genetic and geographical distance of T. ciliata var. pubescens.