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.

1. 隐蔽色（cryptic coloration）的演化往往会响应捕食者施加的选择压力，但高效的种内交流往往又需要一定程度的可被检测性。这便在性选择视觉性状的收益与过度显眼带来的捕食成本之间形成了权衡，而目前学界对高度隐蔽物种如何缓解这一权衡的机制仍知之甚少。2. 本研究以色盲且外观具有隐蔽性的假花园螳螂（false garden mantid，*Pseudomantis albofimbriata*）为研究对象，探究其面临的这类相互冲突的演化需求。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（螳螂自身）、潜在捕食者（鸟类）以及猎物（蜜蜂）的视觉系统中，表征螳螂各躯体区域的显眼度；随后借助状态操控实验与同种选择实验（conspecific choice tests），进一步探究目标颜色性状。3. 视觉建模结果显示，雄性螳螂对同种个体、猎物与捕食者均不具备显眼性——即其在色觉与无彩色维度均具有隐蔽性。与之相对，雌性螳螂在所有潜在接收者的视觉系统中均呈现色觉隐蔽性，但其腹部在无彩色维度却较为显眼。食物操控实验表明，身体状态良好（即卵巢内卵量更多）的雌性，其腹部亮度要高于状态较差的雌性。选择实验结果显示，雄性螳螂始终会被腹部更亮的雌性所吸引。4. 本研究结果揭示了在色盲且经典意义上具有隐蔽性的昆虫中，存在以亮度为媒介的性信号传递。雌性螳螂借助自身唯一可用的视觉通道传递信号，既能向配偶彰显自身品质，又可尽可能降低对捕食者与猎物的显眼程度。此外，雌性螳螂仅通过单一躯体区域传递信号，显然还利用了协同碎裂色（coincident disruptive coloration）进一步降低被潜在窃听者察觉的概率。5. 本研究数据揭示了视觉信号系统中，性选择对显眼性的偏好与自然选择对隐蔽性的需求之间的权衡可通过此种方式得以调解，这是一种全新的案例。这类信号传递模式在外观看似隐蔽的物种中可能十分普遍，而本研究也再次证明，跳出人类视觉的感知能力来分析视觉信号的重要性。