Redpath Museum and Department of Biology, McGill University, 859 Sherbrooke Street West, Montréal, QC, Canada , H3A 2K6.
Philos Trans R Soc Lond B Biol Sci. 2010 Apr 12;365(1543):1041-52. doi: 10.1098/rstb.2009.0314.
Divergence and speciation can sometimes proceed in the face of, and even be enhanced by, ongoing gene flow. We here study divergence with gene flow in Darwin's finches, focusing on the role of ecological/adaptive differences in maintaining/promoting divergence and reproductive isolation. To this end, we survey allelic variation at 10 microsatellite loci for 989 medium ground finches (Geospiza fortis) on Santa Cruz Island, Galápagos. We find only small genetic differences among G. fortis from different sites. We instead find noteworthy genetic differences associated with beak. Moreover, G. fortis at the site with the greatest divergence in beak size also showed the greatest divergence at neutral markers; i.e. the lowest gene flow. Finally, morphological and genetic differentiation between the G. fortis beak-size morphs was intermediate to that between G. fortis and its smaller (Geospiza fuliginosa) and larger (Geospiza magnirostris) congeners. We conclude that ecological differences associated with beak size (i.e. foraging) influence patterns of gene flow within G. fortis on a single island, providing additional support for ecological speciation in the face of gene flow. Patterns of genetic similarity within and between species also suggest that interspecific hybridization might contribute to the formation of beak-size morphs within G. fortis.
在基因流持续存在的情况下，甚至可以促进物种的分化和形成。我们在这里研究具有基因流的达尔文雀的分化，重点研究生态/适应性差异在维持/促进分化和生殖隔离方面的作用。为此，我们调查了加拉帕戈斯群岛圣克鲁斯岛上的 989 只中地雀（Geospiza fortis）的 10 个微卫星基因座的等位基因变异。我们发现不同地点的 G. fortis 之间只有很小的遗传差异。相反，我们发现与喙相关的遗传差异值得注意。此外，在喙大小差异最大的地点，G. fortis 的中性标记也显示出最大的差异，即基因流最低。最后，G. fortis 喙大小形态的形态和遗传分化介于 G. fortis 与其较小的（Geospiza fuliginosa）和较大的（Geospiza magnirostris）近缘种之间。我们得出结论，与喙大小（即觅食）相关的生态差异影响了单个岛屿上 G. fortis 内部的基因流模式，为基因流条件下的生态物种形成提供了额外的支持。种内和种间遗传相似性的模式也表明，种间杂交可能有助于 G. fortis 中喙大小形态的形成。
