Winters Anne E, Green Naomi F, Wilson Nerida G, How Martin J, Garson Mary J, Marshall N Justin, Cheney Karen L
School of Biological Sciences, The University of Queensland, Brisbane, Queensland 4072, Australia
School of Biological Sciences, The University of Queensland, Brisbane, Queensland 4072, Australia.
Proc Biol Sci. 2017 Aug 30;284(1861). doi: 10.1098/rspb.2017.0926.
Warning signal variation is ubiquitous but paradoxical: low variability should aid recognition and learning by predators. However, spatial variability in the direction and strength of selection for individual elements of the warning signal may allow phenotypic variation for some components, but not others. Variation in selection may occur if predators only learn particular colour pattern components rather than the entire signal. Here, we used a nudibranch mollusc, , which exhibits a conspicuous red spot/white body/yellow rim colour pattern, to test this hypothesis. We first demonstrated that secondary metabolites stored within the nudibranch were unpalatable to a marine organism. Using pattern analysis, we demonstrated that the yellow rim remained invariable within and between populations; however, red spots varied significantly in both colour and pattern. In behavioural experiments, a potential fish predator, , used the presence of the yellow rims to recognize and avoid warning signals. Yellow rims remained stable in the presence of high genetic divergence among populations. We therefore suggest that how predators learn warning signals may cause stabilizing selection on individual colour pattern elements, and will thus have important implications on the evolution of warning signals.
警告信号的变化无处不在，但却自相矛盾：低变异性本应有助于捕食者识别和学习。然而，警告信号各个元素的选择方向和强度的空间变异性可能会使某些成分出现表型变异，而其他成分则不会。如果捕食者只学习特定的颜色图案成分而非整个信号，那么选择就可能会出现变异。在此，我们使用一种裸鳃亚目软体动物来检验这一假设，该动物呈现出显眼的红色斑点/白色身体/黄色边缘的颜色图案。我们首先证明，裸鳃亚目动物体内储存的次生代谢物对一种海洋生物来说是不可口的。通过图案分析，我们证明黄色边缘在种群内部和种群之间保持不变；然而，红色斑点在颜色和图案上都有显著变化。在行为实验中，一种潜在的鱼类捕食者利用黄色边缘的存在来识别并避开警告信号。在种群间存在高度遗传差异的情况下，黄色边缘依然保持稳定。因此，我们认为捕食者学习警告信号的方式可能会导致对单个颜色图案元素的稳定选择，从而对警告信号的进化产生重要影响。
