Code from Correlated evolution between colour conspicuousness and drum speed in woodpeckers

Sexual selection drives the evolution of many spectacular animal displays that we see in nature. Yet, how selection combine and elaborate different signal traits remains unclear. Here, we test for correlated evolution between head plumage colour and the drumming behaviour in woodpeckers. These signals function in the context of mate choice and male–male competition, and they may appear to a receiver as a single multimodal display. We test for such correlations in males of 132 species using phylogenetic linear models while considering the effect of habitat. We find that the plumage chromatic contrast is positively correlated with the speed of the drum, supporting the idea that species evolving more conspicuous plumage on their head also evolve faster drum displays. By contrast, we do not find evidence of correlated evolution between the drum speed and head colour diversity, size of the red patch or extent of the plumage achromatic contrast. Drum length was not correlated with any of the plumage coloration metrics. Lastly, we find no evidence that habitat acts as a strong selective force driving the evolution of head coloration or drumming elaboration. Coevolution between different signal modalities is therefore complex, and likely depends on the display components in question.

性选择推动了自然界中诸多令人惊叹的动物通讯展示的演化。然而，选择如何整合并细化不同的信号性状，目前仍未明晰。本研究以啄木鸟为研究对象，检验其头部羽色与叩击行为之间的协同演化关系。这类信号在配偶选择以及雄性间竞争的场景中发挥作用，且接收者可能将其感知为单一的多模态展示。本研究借助系统发育线性模型，同时考量栖息地的影响，对132个物种的雄性个体开展上述相关性检验。研究结果显示，头部羽毛的色彩对比度与叩击速度呈正相关，这支持了如下假说：演化出更醒目头部羽色的物种，其叩击展示的速度也会更快。与之相反，本研究未发现叩击速度与头部色彩多样性、红色斑块大小或羽毛非色彩对比度之间存在协同演化的证据。叩击时长与所有羽色量化指标均无相关性。最后，本研究未发现栖息地作为强选择压力驱动头部羽色或叩击行为细化演化的证据。由此可见，不同信号模态之间的协同演化过程较为复杂，且很可能取决于所关注的展示组分。