Department of Ecology and Genetics, Uppsala University, Uppsala, Sweden.
Evolution. 2012 Apr;66(4):1167-79. doi: 10.1111/j.1558-5646.2011.01518.x. Epub 2011 Dec 14.
Character displacement can reduce costly interspecific interactions between young species. We investigated the mechanisms behind divergence in three key traits-breeding habitat choice, timing of breeding, and plumage coloration-in Ficedula flycatchers. We found that male pied flycatchers became expelled from the preferred deciduous habitat into mixed forest as the superior competitor, collared flycatchers, increased in numbers. The peak in food abundance differs between habitats, and the spatial segregation was paralleled by an increased divergence in timing of breeding between the two species. Male pied flycatchers vary from brown to black with brown coloration being more frequent in sympatry with collared flycatchers, a pattern often proposed to result from selection against hybridization, that is, reinforcement. In contrast to this view, we show that brown male pied flycatchers more often hybridize than black males. Male pied flycatcher plumage coloration influenced the territory obtained in areas of co-occurrence with collared flycatchers, and brown male pied flycatchers experienced higher relative fitness than black males when faced with heterospecific competition. We suggest that allopatric divergence in resource defense ability causes a feedback loop at secondary contact where male pied flycatchers with the most divergent strategy compared to collared flycatchers are favored by selection.
特征替代可以减少年轻物种之间代价高昂的种间相互作用。我们研究了三得利氏雀鹛在三个关键特征上的分歧机制——繁殖栖息地选择、繁殖时间和羽毛颜色。我们发现，随着环颈鸻数量的增加，雄性白腰文鸟被逐出了首选的落叶林栖息地，成为了更具竞争力的竞争者。食物丰富度的峰值在不同的栖息地之间存在差异，而这种空间隔离与两种物种繁殖时间的差异增加是平行的。雄性白腰文鸟的颜色从棕色到黑色不等，棕色在与环颈鸻共存时更为常见，这种模式通常被认为是对杂交的选择，即强化。与这种观点相反，我们表明棕色雄性白腰文鸟比黑色雄性白腰文鸟更容易杂交。雄性白腰文鸟的羽毛颜色影响与环颈鸻共存地区获得的领地，当面临同种竞争时，棕色雄性白腰文鸟比黑色雄性白腰文鸟具有更高的相对适应性。我们认为，资源防御能力的异地分歧在次级接触中产生了一个反馈回路，与环颈鸻相比，具有最具分歧策略的雄性白腰文鸟受到选择的青睐。
