Data from: Background colour matching increases with risk of predation in a colour-changing grasshopper

Cryptic colouration can be adjusted to the local environment by physiological (rapid) change, and/or by morphological (slow) change. The threat-sensitivity hypothesis predicts that the degree of crypsis should respond to the risk of predation (assuming some cost to crypsis). This has not been studied for morphological colour changers, so we manipulated the colour of the rearing substrate (black versus white) and the perceived risk of predation (higher versus lower) for the grasshopper Sphingonotus azurescens. Over a period of several weeks, both nymphs and adults greatly adjusted the brightness of their body towards that of the substrate. Moreover, when individuals were exposed to a greater simulated predation risk (disturbance by hand), they became even more similar in brightness to their substrates, apparently augmenting their degree of crypsis. This study on a morphological colour changer shows that the degree of cryptic colouration (body brightness) is under individual control and appears to change adaptively in response to increased predation risk. In addition, based on analyses of systematic differences in colour in lab-reared offspring, we found indications that even in colour changers there is genetic variation in colouration among individuals, and that populations have diverged adaptively. Such integration of factors determining the cryptic phenotype improves our understanding of the natural selection and constraints imposed on crypsis, which influence both its optimization and evolution.隐蔽色（cryptic colouration）可通过生理（快速）变化和/或形态（慢速）变化适配局部环境。威胁敏感性假说（threat-sensitivity hypothesis）预测，隐蔽性程度应随捕食风险作出响应（前提是获得隐蔽性存在一定代价）。目前针对形态变色物种的相关研究仍较为匮乏，因此本研究以蓝翅蝗（Sphingonotus azurescens）为研究对象，对其饲养基质颜色（黑色与白色）以及感知到的捕食风险（高与低）进行了实验操控。在数周的实验周期内，若虫与成虫均会将自身身体亮度大幅调整至与基质颜色相匹配的水平。此外，当个体暴露于更高的模拟捕食风险（人工惊扰）环境中时，其身体亮度与基质的匹配度会进一步提升，显然是增强了自身的隐蔽性。本项针对形态变色物种的研究表明，隐蔽色程度（身体亮度）受个体自主调控，且会随捕食风险升高作出适应性变化。此外，通过对实验室饲养后代的体色系统性差异进行分析，本研究发现即便在变色物种中，个体间的体色也存在遗传变异，且不同种群已发生适应性分化。这类对隐蔽表型决定因素的整合研究，有助于我们加深对作用于隐蔽性的自然选择与制约机制的理解，而这些机制同时影响着隐蔽性的优化与演化。