Positive feedback between ecological and reproductive character displacement in a young avian hybrid zone

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, i.e. 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 obta...

性状替换（Character displacement）可降低新近分化物种间代价高昂的种间相互作用。本研究以姬鹟属（Ficedula）鹟类为研究对象，探究其3项关键繁殖性状——繁殖栖息地选择、繁殖时序与羽色——的分化机制。研究发现，随着优势竞争者白领姬鹟（collared flycatcher）种群规模扩张，雄性斑姬鹟（pied flycatcher）会从自身偏好的落叶林生境被排挤至混交林生境。不同生境的食物丰度峰值存在显著差异，二者的空间分隔同时伴随繁殖时序分化程度的显著提升。雄性斑姬鹟的羽色呈褐色至黑色的渐变谱系，在与白领姬鹟同域分布的种群中，褐色羽色个体占比更高——这一分布模式以往常被归因于抗杂交选择，即生殖隔离强化（reinforcement）。但本研究结果与该传统观点相悖：相较于黑色羽色雄性斑姬鹟，褐色羽色个体的杂交发生概率显著更高。雄性斑姬鹟的羽色会影响其领地获取（territory acquisition）……