Division of Biology, Imperial College London, Silwood Park, Ascot, Berkshire SL5 7PY, UK.
Philos Trans R Soc Lond B Biol Sci. 2010 Apr 12;365(1543):1077-92. doi: 10.1098/rstb.2009.0281.
Colonization of an archipelago sets the stage for adaptive radiation. However, some archipelagos are home to spectacular radiations, while others have much lower levels of diversification. The amount of gene flow among allopatric populations is one factor proposed to contribute to this variation. In island colonizing birds, selection for reduced dispersal ability is predicted to produce changing patterns of regional population genetic structure as gene flow-dominated systems give way to drift-mediated divergence. If this transition is important in facilitating phenotypic divergence, levels of genetic and phenotypic divergence should be associated. We consider population genetic structure and phenotypic divergence among two co-distributed, congeneric (Genus: Zosterops) bird species inhabiting the Vanuatu archipelago. The more recent colonist, Z. lateralis, exhibits genetic patterns consistent with a strong influence of distance-mediated gene flow. However, complex patterns of asymmetrical gene flow indicate variation in dispersal ability or inclination among populations. The endemic species, Z. flavifrons, shows only a partial transition towards a drift-mediated system, despite a long evolutionary history on the archipelago. We find no strong evidence that gene flow constrains phenotypic divergence in either species, suggesting that levels of inter-island gene flow do not explain the absence of a radiation across this archipelago.
群岛的殖民化为适应辐射奠定了基础。然而，一些群岛拥有壮观的辐射，而另一些则具有较低的多样化水平。种间隔离种群之间的基因流动量是被认为导致这种差异的一个因素。在岛屿殖民鸟类中，选择减少扩散能力预计会导致区域性种群遗传结构的变化模式，因为以基因流为主导的系统让位于漂移介导的分歧。如果这种转变对于促进表型分歧很重要，那么遗传和表型分歧的水平应该相关。我们考虑了生活在瓦努阿图群岛上的两个分布广泛的同种（属：Zosterops）鸟类物种的种群遗传结构和表型分歧。较新的殖民者 Z. lateralis 表现出遗传模式，表明距离介导的基因流有很大影响。然而，不对称基因流动的复杂模式表明种群之间的扩散能力或倾向存在差异。地方性物种 Z. flavifrons 尽管在群岛上有很长的进化历史，但仅向漂移介导的系统部分过渡。我们没有强有力的证据表明基因流动限制了这两个物种的表型分歧，这表明岛屿间的基因流动水平并不能解释为什么这个群岛没有发生辐射。
