Nielsen L R
Biological Institute, University of Copenhagen, Øster Farimagsgade 2D, DK-1353 Copenhagen K, Denmark.
Heredity (Edinb). 2004 Nov;93(5):434-42. doi: 10.1038/sj.hdy.6800520.
Molecular variance was estimated in seven populations of the endemic species Scalesia affinis within and among islands of the Galapagos. The analysis, based on 157 polymorphic AFLP markers, revealed a high differentiation among populations, of which most was partitioned among islands. In addition, the information content of AFLP markers was tested with sets of discriminant analyses based on different numbers of AFLP markers. This indicated that the markers were highly informative in discriminating the populations. Although one of four populations from the island Isabela was sampled from a volcano 100 km away from the remaining populations, this population resembled the others on Isabela. The partitioning of molecular variance (AFLP) resulted in two unities, one consisting of populations from Isabela and one of populations from Santa Cruz and Floreana. The differentiation in two chloroplast microsatellites was higher than for AFLP markers and equally partitioned among populations within islands as among islands. Thus, gene flow via fruits within islands is as limited as among islands. The lower differentiation within islands in the nuclear AFLP markers may thus indicate that gene flow within islands is mostly accounted for by pollen transfer. S. affinis is the only species in the genus that is not listed in 2000 IUCN Red List of Threatened Species. However, due to prominent grazing and land exploitation, some populations have recently been reduced markedly, which was reflected in lower diversity. As inbreeding depression is present in the species, the rapid bottlenecks are threats to the populations.
对加拉帕戈斯群岛各岛屿内及岛屿间的特有物种近缘鳞苞菊的七个种群进行了分子变异估计。基于157个多态性AFLP标记的分析显示，种群间存在高度分化，其中大部分分化存在于岛屿之间。此外，基于不同数量的AFLP标记，通过判别分析集对AFLP标记的信息含量进行了测试。这表明这些标记在区分种群方面具有很高的信息量。尽管来自伊莎贝拉岛的四个种群中有一个是从距离其他种群100公里的一座火山上采集的，但该种群与伊莎贝拉岛上的其他种群相似。分子变异（AFLP）的划分产生了两个单元，一个由来自伊莎贝拉岛的种群组成，另一个由来自圣克鲁斯岛和弗洛雷阿纳岛的种群组成。两个叶绿体微卫星的分化高于AFLP标记，并且在岛屿内种群间的分布与岛屿间的分布相同。因此，通过果实进行的岛内基因流动与岛屿间的基因流动一样有限。核AFLP标记在岛内较低的分化可能表明，岛内的基因流动主要是由花粉传播造成的。近缘鳞苞菊是该属中唯一未被列入2000年《世界自然保护联盟濒危物种红色名录》的物种。然而，由于显著的放牧和土地开发，一些种群最近明显减少，这反映在较低的多样性上。由于该物种存在近亲繁殖衰退现象，快速的瓶颈效应是对种群的威胁。
