Data from: What makes a multimodal signal attractive? A preference function approach

Courtship signals are often complex and include components within and across sensory modalities. Unfortunately, the evidence for how multimodal signals affect female preference functions is still rather limited. This is an important scientific gap because preference function shape can indicate which male traits are under the strongest selection. We modeled how preference function shape can be altered under four scenarios of varying signal content, including both redundant and non-redundant signals. The model was tested with the brown-headed cowbird (Molothrus ater); we manipulated male song attractiveness and visual display intensity, and assessed female preferences in an audiovisual playback study. We found that the intensity of a visual display can modify how attractive a song is for females. This indicates that the visual and acoustic male signal components are non-redundant and modulate each other. Our study shows a change in the direction of female preference functions for one signaling modality resulting from changes in the attractiveness of the other modality. Overall, our findings suggest that male signals in this species may not be under the typical directional selection documented in other species, but rather selection may favor males that possess a range of different signals that can be used strategically during different social contexts.

求偶信号往往结构复杂，既包含单模态信号组分，也涵盖跨模态信号组分。遗憾的是，目前关于多模态信号（multimodal signals）如何调控雌性偏好函数（female preference functions）的实证研究仍较为匮乏。这一研究空白具有重要科学价值，因为偏好函数的形态可用于揭示哪些雄性性状正承受最强的选择压力。本研究针对信号内容存在差异的四种情境（涵盖冗余信号与非冗余信号两类），构建了偏好函数形态变化的理论模型。本研究以棕头牛鹂（Molothrus ater）为实验对象，通过调控雄性鸣唱的吸引力与视觉展示的强度，并利用音视频回放实验评估雌性择偶偏好，对该模型进行了验证。研究结果表明，视觉展示的强度能够改变雌性对雄性鸣唱的吸引力评价，这说明雄性的视觉与声学信号组分并非冗余，而是存在相互调控的关系。本研究证实，单一信号模态的雌性偏好函数方向，会因另一信号模态的吸引力变化而发生改变。综合来看，本研究结果表明，该物种的雄性求偶信号可能并未经受其他物种中常见的定向选择（directional selection），反而更倾向于选择那些拥有多种不同信号、可在不同社会情境中策略性运用的雄性个体。