Department of Biology, Queen's University, Kingston, ON, Canada.
J Evol Biol. 2021 Jul;34(7):1110-1124. doi: 10.1111/jeb.13798. Epub 2021 Jun 29.
Signal divergence is thought to reduce the costs of co-occurrence for closely related species and may thereby be important in the generation and maintenance of new biodiversity. In birds, closely related, sympatric species are more divergent in their colour patterns than those that live apart, but the selective pressures driving sympatric divergence in colour pattern are not well-understood. Here, we conducted field experiments on naïve birds using spectrometer-matched, painted, 3D-printed models to test whether selection against heterospecific aggression might drive colour pattern divergence in the genus Poecile. We found that territorial male black-capped chickadees (P. atricapillus) are equally likely to attack sympatric and allopatric congeners, and wintering flocks are equally likely to visit feeders occupied by sympatric and allopatric congeners, despite sympatric congeners being more divergent in colour pattern. These results suggest that either the concerted evolution of additional traits (e.g. discrimination), or interactions in sympatry that promote learning, is required if colour pattern divergence among sympatric species is to reduce heterospecific aggression. Alternatively, colour pattern divergence among sympatric species may be caused by other selective pressures, such as selection against hybridization or habitat partitioning and secondary signal adaptation.
信号分歧被认为可以降低密切相关物种共同出现的成本，因此可能在新生物多样性的产生和维持中发挥重要作用。在鸟类中，生活在同一地区的密切相关的同种物种的颜色图案比那些生活在不同地区的物种更加多样化，但导致颜色图案在同一地区发生分歧的选择压力还没有得到很好的理解。在这里，我们使用光谱仪匹配的、绘制的、3D 打印的模型对天真的鸟类进行了野外实验，以测试针对异性攻击的选择是否可能导致 Poecile 属的颜色图案发生分歧。我们发现，领地性的雄性黑顶山雀（P. atricapillus）同样可能攻击同域和异域的同类，冬季的鸟群同样可能访问由同域和异域同类占据的喂食器，尽管同域的同类颜色图案的分歧更大。这些结果表明，如果同域物种之间的颜色图案分歧要减少异性攻击，那么可能需要协同进化额外的特征（例如识别），或者在同域中促进学习的相互作用。或者，同域物种之间的颜色图案分歧可能是由其他选择压力引起的，例如对杂交或栖息地分割和二级信号适应的选择。
