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.

中文翻译：

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对作为鸟类颜色模式分歧驱动因素的异种特异性攻击的选择实验测试。

信号发散被认为可以降低密切相关物种共存的成本，因此可能对新生物多样性的产生和维持很重要。在鸟类中，密切相关的同域物种在颜色模式上的差异比分开居住的物种更大，但驱动同域物种颜色模式差异的选择压力尚不清楚。在这里，我们使用光谱仪匹配的、涂漆的、3D 打印的模型对幼稚的鸟类进行了现场实验，以测试针对异种特异性攻击的选择是否可能导致 Poecile 属的颜色模式差异。我们发现领地雄性黑顶山雀（P. atricapillus）攻击同域和异域同源物的可能性相同，和越冬的羊群同样有可能访问被同域和异域同族群占据的饲养者，尽管同域同族群在颜色模式上更加不同。这些结果表明，如果同域物种之间的颜色模式差异要减少异种特异性攻击，则需要额外特征（例如歧视）的协同进化或促进学习的同域相互作用。或者，同域物种之间的颜色模式差异可能是由其他选择压力引起的，例如选择反对杂交或栖息地划分和次要信号适应。如果同域物种之间的颜色模式差异要减少异种攻击，则需要促进学习的同域中的相互作用。或者，同域物种之间的颜色模式差异可能是由其他选择压力引起的，例如选择反对杂交或栖息地划分和次要信号适应。如果同域物种之间的颜色模式差异要减少异种攻击，则需要促进学习的同域中的相互作用。或者，同域物种之间的颜色模式差异可能是由其他选择压力引起的，例如选择反对杂交或栖息地划分和次要信号适应。