Data from: Conspicuous signal evolution in heterogeneous environments

A fundamental prediction of reproductive signal evolution is that selection should favor male courtship signals that are conspicuous with respect to the surrounding media. However, many species live in heterogeneous environments where spatiotemporal variability can degrade the efficacy of signals tuned to specific conditions. One rarely considered solution to this problem is to evolve generalized signals that can effectively transmit information under most of the conditions that are likely to be encountered. Here, I present results from a study of a freshwater fish, the brook stickleback (Culaea inconstans) that are consistent with the hypothesis that sexually dimorphic body coloration has been driven by selection for conspicuousness under multiple environmental conditions. In choice tests, females showed no bias favoring a conspicuous black stimulus in simulated oligotrophic stream conditions, but showed a strong and equal bias for the black phenotype in simulated dystrophic and eutrophic streams. These data indicate that the evolution of signals that maximize achromatic contrast with the surrounding environment may be an effective mechanism for maintaining conspicuousness in heterogeneous visual environments. The repeated evolution of black color signals by stream fishes may therefore represent a specific example of this general evolutionary mechanism.

繁殖信号演化的一项核心预测是：自然选择会青睐那些相对于周围传播介质更具辨识度的雄性求偶信号。然而，诸多物种栖息于异质环境中，这类环境的时空变异会削弱针对特定条件优化的信号的传播效能。针对该问题的一项鲜有被探讨的解决方案，是演化出可在多数大概率遭遇的环境条件下有效传递信息的通用信号。本研究以淡水鱼类溪刺鱼（Culaea inconstans）为对象，其研究结果与下述假说一致：雌雄异形的体色演化，是受多重环境条件下对信号辨识度的自然选择所驱动的。在选择实验中，雌性个体在模拟贫营养溪流的环境下，并未表现出对醒目黑色刺激的偏好；但在模拟腐殖质营养与富营养溪流的环境中，均对黑色表型表现出强烈且程度相当的偏好。上述数据表明，最大化与周围环境的无彩色对比度的信号演化，或许是在异质视觉环境中维持信号辨识度的有效机制。因此，溪流鱼类反复演化出黑色信号的现象，或可作为该通用演化机制的一个具体实例。