The sensory drive hypothesis states that selection acts on signals to make them more detectable in the habitat conditions in which they occur, resulting in signal divergence for species occupying different habitats. For colour signals, visibility depends on the luminance contrast and the chromatic contrast between the signal and the viewing background. Sensory drive has been tested in studies of the colourful dewlaps of anolines occupying different habitats. These studies found that red or orange dewlaps were more visible than yellow or white dewlaps across all habitat types, counter to the predictions of sensory drive that a species’ signal should be more visible in its own habitat than in habitats of other species. However, in these, and other sensory drive studies, chromatic contrast was calculated with a visual perception model that assumed that total light intensity has little or no effect on chromatic contrast perception. We carried out behavioural experiments testing the probability of detection of green, yellow and red stimuli presented against luminance-matched green backgrounds, at low and high light intensity typical of shaded and unshaded habitats. We found that the red stimulus was most detectable in the high light condition, while in low light, yellow and red stimuli were equally detectable. We modelled the stimuli with a receptor noise model that takes total light intensity into account. The model predictions were consistent with the behaviour results. We conclude that there is an important interaction between total light intensity and chromatic contrast in determining the visibility of colour signals, which should be taken into account in visual ecology studies. For animals with small eyes, shade level, which strongly influences total light intensity, may be as important as, or more important than habitat spectral quality in the evolution of signal colour diversity through sensory drive.

中文翻译：

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总光强和色度对比度对 Anolis 蜥蜴视觉信号可见度的交互作用

感官驱动假说指出，选择作用于信号，使它们在它们发生的栖息地条件下更容易被检测到，从而导致占据不同栖息地的物种的信号发散。对于彩色信号，可见度取决于信号与观察背景之间的亮度对比度和色度对比度。感官驱动已在对占据不同栖息地的 anolines 的彩色赘肉的研究中进行了测试。这些研究发现，在所有栖息地类型中，红色或橙色的赘肉比黄色或白色的赘肉更明显，这与感官驱动的预测相反，即一个物种的信号在其自身的栖息地中应该比在其他物种的栖息地中更明显。然而，在这些和其他感官驱动研究中，色度对比度是用视觉感知模型计算的，该模型假设总光强度对色度对比度感知几乎没有影响。我们进行了行为实验，测试在阴影和无阴影栖息地典型的低光和高光强度下，针对亮度匹配的绿色背景呈现的绿色、黄色和红色刺激的检测概率。我们发现红色刺激在高光条件下最容易被检测到，而在低光下，黄色和红色刺激同样可检测到。我们使用受体噪声模型对刺激进行建模，该模型考虑了总光强度。模型预测与行为结果一致。我们得出结论，在确定颜色信号的可见性时，总光强度和色度对比度之间存在重要的相互作用，在视觉生态学研究中应该考虑到这一点。对于小眼睛的动物，强烈影响总光强度的阴影水平在通过感官驱动的信号颜色多样性演变中可能与栖息地光谱质量一样重要，或更重要。