Kang Changku, Zahiri Reza, Sherratt Thomas N
Department of Biology, Carleton University, Ottawa, Ontario K1S 5B6, Canada
Canadian Food Inspection Agency, Ottawa, Ontario K1A 0Y9, Canada.
Proc Biol Sci. 2017 Aug 30;284(1861). doi: 10.1098/rspb.2017.1287.
Many cryptic prey have also evolved hidden contrasting colour signals which are displayed to would-be predators. Given that these hidden contrasting signals may confer additional survival benefits to the prey by startling/intimidating predators, it is unclear why they have evolved in some species, but not in others. Here, we have conducted a comparative phylogenetic analysis of the evolution of colour traits in the family Erebidae (Lepidoptera), and found that the hidden contrasting colour signals are more likely to be found in larger species. To understand why this relationship occurs, we present a general mathematical model, demonstrating that selection for a secondary defence such as deimatic display will be stronger in large species when (i) the primary defence (crypsis) is likely to fail as its body size increases and/or (ii) the secondary defence is more effective in large prey. To test the model assumptions, we conducted behavioural experiments using a robotic moth which revealed that survivorship advantages were higher against wild birds when the moth has contrasting hindwings and large size. Collectively, our results suggest that the evolutionary association between large size and hidden contrasting signals has been driven by a combination of the need for a back-up defence and its efficacy.
许多具有保护色的猎物还进化出了隐藏的对比色信号，这些信号会展示给潜在的捕食者。鉴于这些隐藏的对比信号可能通过惊吓/威慑捕食者为猎物带来额外的生存优势，目前尚不清楚为什么它们在某些物种中进化出来，而在其他物种中却没有。在这里，我们对灯蛾科（鳞翅目）颜色特征的进化进行了比较系统发育分析，发现隐藏的对比色信号更有可能出现在体型较大的物种中。为了理解这种关系为何会出现，我们提出了一个通用的数学模型，证明当（i）随着体型增大，主要防御（保护色）可能失效，和/或（ii）次要防御在大型猎物中更有效时，对诸如恫吓展示等次要防御的选择在大型物种中会更强。为了检验模型假设，我们使用机器蛾进行了行为实验，结果显示当蛾具有对比鲜明的后翅和较大体型时，其在对抗野生鸟类时的生存优势更高。总体而言，我们的结果表明，体型较大与隐藏的对比信号之间的进化关联是由对后备防御的需求及其有效性共同驱动的。
