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 color patterns than those that live apart, but the selective pressures driving sympatric divergence in color 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 color 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 color pattern. These results suggest that either the concerted evolution of additional traits (e.g., discrimination), or interactions in sympatry that promote learning, are required if color pattern divergence among sympatric species is to reduce heterospecific aggression. Alternatively, color 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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针对异种侵略作为鸟类颜色模式差异的驱动因素的选择实验。

信号发散被认为减少了密切相关物种的共现成本，因此可能在新生物多样性的产生和维持中很重要。在密切相关的鸟类中，同胞属物种的颜色模式比分开生活的物种更趋异，但是驱动同胞物种的颜色模式产生的选择压力还没有被很好地理解。在这里，我们使用光谱仪匹配的彩绘3D打印模型在幼稚的鸟类上进行了野外实验，以测试针对异源性侵略的选择是否可能导致Poecile属的颜色模式发散。我们发现，领土雄性黑冠山雀（P. atricapillus）同样有可能攻击同胞和同种异体的同类动物，越冬的鸡群也有可能拜访同胞和同种异体的同类动物所占据的饲养者，尽管同胞同源物在颜色模式上差异更大。这些结果表明，如果同胞物种之间的颜色模式差异是为了减少异源性侵略，则需要其他特征的协同进化（例如，歧视），或在交联系统中促进学习的相互作用。可替代地，同胞物种之间的颜色图案差异可能是由其他选择性压力引起的，例如对杂交或栖息地划分的选择以及对次要信号的适应。