Department of Biological Sciences, University of Cyprus, Nicosia 1678, Cyprus.
Evolution. 2011 Nov;65(11):3162-74. doi: 10.1111/j.1558-5646.2011.01386.x. Epub 2011 Sep 20.
Geographic isolation in rainforest refugia and local adaptation to ecological gradients may both be important drivers of evolutionary diversification. However, their relative importance and the underlying mechanisms of these processes remain poorly understood because few empirical studies address both putative processes in a single system. A key question is to what extent is divergence in signals that are important in mate and species recognition driven by isolation in rainforest refugia or by divergent selection across ecological gradients? We studied the little greenbul, Andropadus virens, an African songbird, in Cameroon and Uganda, to determine whether refugial isolation or ecological gradients better explain existing song variation. We then tested whether song variation attributable to refugial or ecological divergence was biologically meaningful using reciprocal playback experiments to territorial males. We found that much of the existing song variation can be explained by both geographic isolation and ecological gradients, but that divergence across the gradient, and not geographic isolation, affects male response levels. These data suggest that ecologically divergent traits, independent of historical isolation during glacial cycles, can promote reproductive isolation. Our study provides further support for the importance of ecology in explaining patterns of evolutionary diversification in ecologically diverse regions of the planet.
地理隔离在雨林避难所和对生态梯度的局部适应可能都是进化多样化的重要驱动因素。然而，这些过程的相对重要性和潜在机制仍然知之甚少，因为很少有实证研究在单个系统中同时解决这两个假设过程。一个关键问题是，在对配偶和物种识别很重要的信号的分歧中，有多少是由雨林避难所的隔离驱动的，还是由生态梯度的分歧选择驱动的？我们在喀麦隆和乌干达研究了小绿雀（Andropadus virens），这是一种非洲鸣禽，以确定避难所隔离还是生态梯度更能解释现有的歌声变化。然后，我们通过对领地雄性进行回播实验，测试归因于避难所或生态分歧的歌声变化是否具有生物学意义。我们发现，现有的大部分歌声变化可以用地理隔离和生态梯度来解释，但梯度上的分歧，而不是地理隔离，会影响雄性的反应水平。这些数据表明，与冰川周期期间的历史隔离无关的生态差异特征可以促进生殖隔离。我们的研究进一步支持了生态学在解释地球上生态多样化地区进化多样化模式中的重要性。
