Freville H, Justy F, Olivieri I
Université Montpellier 2, ISEM, CC065, F-34095 Montpellier cedex 05, France.
Mol Ecol. 2001 Apr;10(4):879-89. doi: 10.1046/j.1365-294x.2001.01249.x.
Centaurea corymbosa Pourret (Asteraceae) is a narrow endemic species known only from six populations located in a 3-km2 area in the south of France. Earlier field experiments have suggested that pollen and seed dispersal were highly restricted within and among populations. Consistent with the field results, populations were highly differentiated for five allozyme loci and among-population variation fitted an isolation-by-distance model. In the present study, we investigated the genetic structure of C. corymbosa using six microsatellite loci. As with allozymes, microsatellites revealed no within-population structure and a large differentiation among populations. However, allozyme loci were less powerful than microsatellites in detecting the extent of gene flow assessed by assignment tests. The patterns of structuration greatly varied among loci for both types of marker; we suggest that differences in single-locus pattern could mainly be an effect of stochastic variation for allozymes and an effect of variation in mutation rate for microsatellites. In contrast to the multilocus results, the two most polymorphic microsatellite loci did not show any isolation-by-distance pattern. Our results suggest that highly variable loci might not always be the best suited markers to quantify levels of gene flow among populations.
伞房矢车菊（Centaurea corymbosa Pourret，菊科）是一种狭域特有物种，仅在法国南部一个面积为3平方公里的区域内的六个种群中被发现。早期的野外实验表明，花粉和种子传播在种群内部和种群之间受到高度限制。与野外结果一致，五个等位酶位点在种群间高度分化，种群间变异符合距离隔离模型。在本研究中，我们使用六个微卫星位点研究了伞房矢车菊的遗传结构。与等位酶一样，微卫星显示种群内部没有结构，种群间有很大分化。然而，在通过分配测试评估基因流动程度方面，等位酶位点不如微卫星有效。两种标记类型的位点间结构模式差异很大；我们认为单一位点模式的差异主要是等位酶随机变异的结果，以及微卫星突变率变异的结果。与多位点结果相反，两个多态性最高的微卫星位点没有显示任何距离隔离模式。我们的结果表明，高度可变的位点可能并不总是最适合量化种群间基因流动水平的标记。
