Data from: Sexual signals for the colour-blind: cryptic female mantids signal quality through brightness

1. Cryptic coloration may evolve in response to selective pressure imposed by predators, yet effective intraspecific communication may require some level of detectability. This creates a tension between the benefits of sexually selected visual traits and the predatory costs imposed by greater conspicuousness, and little is known about how this tension may be ameliorated in highly cryptic species. 2. We explore these competing demands in the false garden mantid Pseudomantis albofimbriata, a colour-blind and seemingly cryptic insect. We use reflectance spectrometry and receptor-noise modelling to characterize the conspicuousness of mantid body regions in the visual systems of mates (mantids), as well as potential predators (birds) and prey (bees). We then use condition manipulation and conspecific choice tests to further explore the colour traits of interest. 3. Based on visual modelling, we find that male mantids are inconspicuous to conspecifics, prey and predators – that is, they are chromatically and achromatically cryptic. In contrast, female mantids are chromatically cryptic to all potential receivers, but their abdomens are achromatically conspicuous. Our food manipulation experiment shows that females in good condition (and therefore with more eggs) have brighter abdomens than females in poor condition. Choice assays show male mantids are consistently attracted to females bearing brighter abdomens. 4. Our results reveal brightness-mediated sexual signalling in a colour-blind and classically cryptic insect. By communicating in the only visual channel available to them, female mantids are conspicuously signalling their quality to mates, while potentially minimizing their conspicuousness to predators and prey. Furthermore, by signalling with only a single body region, female mantids are apparently using coincident disruptive coloration to further decrease detectability to potential eavesdroppers. 5. Our data reveal a novel example of the way in which the trade-off between sexual selection for conspicuousness and natural selection for crypsis may be mediated in a visual signalling system. Such signals may be common in apparently cryptic species, and this study once again demonstrates the importance of analysing visual signals beyond the capacity of human vision.

Usage Notes
Choice testsData from conspecific choice experimentchoice_tests.csvCondition and brightnessData from female condition/brightness experimentcondition_brightness.csvVisual modellingData from visual modelling of mantid body regionsvisual_modelling.csv

1. 保护色（cryptic coloration）可因捕食者施加的选择压力演化，但有效的种内交流往往需要一定程度的被检测性。这便在性选择带来的视觉性状收益，与更高显眼度引发的捕食风险成本之间形成了权衡，而针对高度隐蔽物种如何缓解这一权衡的研究仍寥寥无几。
2. 本研究以假花园螳螂（Pseudomantis albofimbriata）——一种色盲且外观高度隐蔽的昆虫——为对象，探究这两种对立的选择压力。我们通过反射光谱法（reflectance spectrometry）与受体噪声模型（receptor-noise modelling），分别在配偶（同种螳螂）、潜在捕食者（鸟类）以及猎物（蜜蜂）的视觉系统中，表征螳螂身体各区域的显眼度。随后我们开展条件操控实验与同种选择试验，进一步探究目标颜色性状。
3. 视觉建模结果显示，雄性螳螂在同种个体、猎物与捕食者的视觉系统中均不显眼，即其在色度与无彩色层面均具备隐蔽性。与之相对，雌性螳螂在所有潜在接收者的视觉系统中均色度隐蔽，但腹部在无彩色层面较为显眼。食物操控实验表明，身体状态良好（即怀卵量更高）的雌性个体，其腹部亮度显著高于状态较差的雌性。选择试验结果显示，雄性螳螂会持续偏好腹部亮度更高的雌性个体。
4. 本研究结果揭示了在色盲且经典隐蔽性昆虫中，基于亮度的性信号交流机制。雌性螳螂通过自身仅有的视觉通道传递信号，既向配偶明确传递了自身质量的信号，同时尽可能降低了对捕食者与猎物的显眼程度。此外，雌性螳螂仅通过单一身体区域传递信号，显然利用了重合混淆色（disruptive coloration），进一步降低了被潜在窃听者检测到的概率。
5. 本研究的数据揭示了一个全新案例，展示了性选择对显眼度的偏好，与自然选择对隐蔽性的要求之间的权衡，可如何在视觉信号系统中得到协调。这类信号在外观看似隐蔽的物种中可能十分常见，本研究也再次证明，超越人类视觉能力的视觉信号分析具有重要意义。

使用说明
选择试验：同种选择实验数据，对应文件为choice_tests.csv
身体状态与亮度：雌性身体状态/亮度实验数据，对应文件为condition_brightness.csv
视觉建模：螳螂身体区域视觉建模分析数据，对应文件为visual_modelling.csv