Department of Biosciences, Mokpo National University, Muan, South Korea.
Department of Agricultural Biotechnology, Seoul National University, Seoul, South Korea.
J Evol Biol. 2023 Jul;36(7):1032-1039. doi: 10.1111/jeb.14153. Epub 2023 Feb 3.
Countershading is a gradient of colouration in which the illuminated dorsal surfaces are darker than the unilluminated ventral surface. It is widespread in the animal kingdom and endows the body with a more uniform colour to decrease the chance of detection by predators. Although recent empirical studies support the theory of survival advantage conferred by countershading, this camouflage strategy has evolved only in some of the cryptic animals, and our understanding of the factors that affect the evolution of countershading is limited. This study examined the association between body size and countershading using lepidopteran larvae (caterpillars) as a model system. Specifically, we predicted that countershading may have selectively evolved in large-sized species among cryptic caterpillars if (1) large size constrains camouflage which facilitates the evolution of a trait reinforcing their crypsis and (2) the survival advantage of countershading is size-dependent. Phylogenetic analyses of four different lepidopteran families (Saturniidae, Sphingidae, Erebidae, and Geometridae) suggest equivocal results: countershading was more likely to be found in larger species in Saturniidae but not in the other families. The field predation experiment assuming avian predators did not support size-dependent predation in countershaded prey. Collectively, we found only weak evidence that body size is associated with countershading in caterpillars. Our results suggest that body size is not a universal factor that has shaped the interspecific variation in countershading observed in caterpillars.
体侧颜色对比是一种颜色梯度，其中受光的背部表面比不受光的腹部表面更暗。它在动物王国中广泛存在，使身体呈现更均匀的颜色，从而降低被捕食者发现的机会。尽管最近的实证研究支持了体侧颜色对比带来生存优势的理论，但这种伪装策略仅在一些隐蔽动物中进化而来，我们对影响体侧颜色对比进化的因素的理解是有限的。本研究使用鳞翅目幼虫（毛毛虫）作为模型系统，研究了体型与体侧颜色对比之间的关系。具体而言，我们预测，如果（1）大尺寸限制了伪装，从而促进了强化其隐蔽性的特征的进化，以及（2）体侧颜色对比的生存优势与体型相关，那么在隐蔽性毛毛虫的大型物种中可能会选择性地进化出体侧颜色对比。对四个不同的鳞翅目科（天蚕科、大蚕蛾科、夜蛾科和尺蛾科）的系统发育分析得出了模棱两可的结果：在天蚕科中，体侧颜色对比更可能出现在较大的物种中，但在其他科中则不然。假设鸟类捕食者的野外捕食实验并不支持具有体侧颜色对比的猎物在体型上的捕食依赖关系。总的来说，我们只发现了微弱的证据表明，体型与毛毛虫的体侧颜色对比有关。我们的结果表明，体型并不是影响毛毛虫体侧颜色对比种间变异的普遍因素。
