Data from: Phenotypic plasticity drives a depth gradient in male conspicuousness in threespine stickleback, Gasterosteus aculeatus

Signal evolution is thought to depend on both a signal's detectability or conspicuousness (signal design) as well as any extractable information it may convey to a potential receiver (signal content). While theoretical and empirical work in sexual selection has largely focused on signal content, there has been a steady accrual of evidence that signal design is also important for trait evolution. Despite this, relatively little attention has been paid to spatial variation in the conspicuousness of a given signal, especially over small spatial scales (relative to an organism's dispersal distance). Here, we show that visual signals of male threespine stickleback vary in conspicuousness, depending on a male's nest depth within a given lake. Deeper-nesting males were typically more chromatically conspicuous than shallow nesting males. This trend is partly because all male stickleback are more conspicuous in deep optical environments. However, deep males are even more conspicuous than environmentally-driven null expectations, while shallow males tend to be disproportionally cryptic. Experimental manipulation of male nesting depth induced plastic changes in nuptial color that replicated the natural gradients in conspicuousness. We discuss a number of potential mechanisms that could produce depth gradients in conspicuousness in male stickleback, including concomitant depth gradients in diet, predation pressure, male/female density, female preference and opportunity for sexual selection.

信号演化被认为同时取决于信号的可检测性或显眼度（信号设计，signal design），以及其向潜在接收者传递的所有可提取信息（信号内容，signal content）。尽管性选择领域的理论与实证研究大多聚焦于信号内容，但日益增多的证据表明，信号设计对性状演化同样至关重要。尽管如此，针对特定信号的显眼度空间变异的研究仍较为匮乏，尤其是在相较于生物扩散距离的小空间尺度上。本研究表明，雄性三棘刺鱼（threespine stickleback）的视觉信号显眼度存在差异，这种差异取决于其在特定湖泊中的筑巢深度。筑巢深度较深的雄性通常比筑巢较浅的雄性具有更高的色彩显眼度。这一趋势部分源于所有雄性三棘刺鱼在深水光学环境中的显眼度更高。然而，筑巢较深的雄性的显眼度甚至高于环境驱动的零假设预期，而筑巢较浅的雄性则往往不成比例地更为隐蔽。通过对雄性筑巢深度进行实验操控，可诱导其婚姻色（nuptial color）发生可塑性变化，该变化重现了自然状态下的显眼度梯度。我们讨论了多种可能导致雄性三棘刺鱼显眼度随深度产生梯度变化的潜在机制，包括伴随深度梯度变化的饮食、捕食压力、雌雄密度、雌性偏好以及性选择机会等。