Conspicuous colour patterns of animals, such as dots or stripes, can function as sexual and/or social signals. Their evolution is often explained by honest indicator mechanisms or the sensory exploitation hypothesis. In birds, however, the latter scenario has been scarcely tested. According to the sensory exploitation hypothesis, prey-like colour patterns can evolve when they contribute to attracting opposite-sex conspecifics by hitchhiking pre-existing sensory systems (sensory bias) that help foraging. Even without cheating scenarios, visual systems can serve as an underlying factor that facilitates the evolution of both foraging behaviours and colour patterns on the body. To test this idea, we examined the relationship between bird plumage patterns and diet using phylogenetic comparative approaches. Specifically, we focused on white polka-dot plumage patterns in estrildid finches and tested whether such patterns evolved for visual sensory systems that help foraging termites and other gregarious whitish small round prey items. Although we predicted that white polka-dots exist in termite-eater species, and that termite-eating evolved before the white polka-dot pattern, ancestral reconstruction did not reveal clear ancestral states for termite-eating. However, the phylogenetic regression model showed that species with conspicuous white polka-dots tended to be termite-eaters. We also found that estrildids with white polka-dots were likely to become termite-eaters, while those without white polka-dots were likely to become non-termite eaters, according to evolutionary transition analysis. These results are in contrast to the prediction of sensory exploitation hypothesis, wherein diet is believed to trigger the evolution of plumage patterns. However, the results presented here suggest that pre-existing sensory bias for white dots may have promoted the evolution of both termite-eating and white polka-dot plumage patterns in estrildids.

中文翻译：

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感官偏差在羽毛图案进化中的潜在作用：白蚁食性和雌雀雀的圆点

动物的显眼颜色图案，例如点或条纹，可以作为性和/或社交信号。它们的进化通常可以用诚实的指标机制或感官开发假设来解释。然而，在鸟类中，后一种情况几乎没有经过测试。根据感官开发假说，当它们通过搭便车帮助觅食的预先存在的感官系统（感官偏见）来吸引异性同种动物时，类似猎物的颜色模式可以进化。即使没有作弊场景，视觉系统也可以作为促进觅食行为和身体颜色模式进化的潜在因素。为了测试这个想法，我们使用系统发育比较方法检查了鸟类羽毛模式和饮食之间的关系。具体来说，我们专注于 estrildid 雀的白色圆点羽毛图案，并测试这些图案是否进化为视觉感官系统，有助于觅食白蚁和其他群居的白色圆形小猎物。尽管我们预测白蚁食性物种中存在白色圆点，并且白蚁食在白色圆点图案之前进化，但祖先重建并未揭示白蚁食的明确祖先状态。然而，系统发育回归模型表明，具有明显白色圆点的物种往往是白蚁食者。我们还发现，根据进化转变分析，带有白色圆点花纹的 estrildids 很可能成为白蚁食者，而那些没有白色圆点花纹的 estrildids 很可能成为非白蚁食者。这些结果与感官开发假说的预测相反，其中饮食被认为触发了羽毛模式的进化。然而，这里呈现的结果表明，对白点的预先存在的感官偏见可能促进了雌蜂科动物吃白蚁和白色圆点羽毛图案的进化。