Postema Elizabeth G
Department of Entomology and Nematology, University of California, Davis, CA 95616, USA.
Curr Zool. 2021 Oct 4;68(4):451-458. doi: 10.1093/cz/zoab082. eCollection 2022 Aug.
When constraints on antipredator coloration shift over the course of development, it can be advantageous for animals to adopt different color strategies for each life stage. Many caterpillars in the genus exhibit unique ontogenetic color sequences: for example, early instars that masquerade as bird feces, with later instars possessing eyespots. I hypothesize that larvae abandon feces masquerade in favor of eyespots due to ontogenetic changes in signaler size. This ontogenetic pattern also occurs within broader seasonal shifts in background color and predator activity. I conducted predation experiments with artificial prey to determine how potential signaling constraints (specifically size and season) shape predation risk, and consequently the expression of ontogenetic color change in larvae. Seasonally, both predation and background greenness declined significantly from July to September, though there was little evidence that these patterns impacted the effectiveness of either color strategy. Caterpillar size and color strongly affected the attack rate of avian predators: attacks increased with prey size regardless of color, and eyespotted prey were attacked more than masquerading prey overall. These results may reflect a key size-mediated tradeoff between conspicuousness and intimidation in eyespotted prey, and raise questions about how interwoven aspects of behavior and signal environment might maintain the prevalence of large, eyespotted larvae in nature.
当反捕食者体色的限制在发育过程中发生变化时，动物在每个生命阶段采取不同的颜色策略可能是有利的。该属中的许多毛虫表现出独特的个体发育颜色序列：例如，早期幼虫伪装成鸟粪，后期幼虫则具有眼斑。我推测，由于信号发出者大小的个体发育变化，幼虫放弃粪便伪装而选择眼斑。这种个体发育模式也发生在背景颜色和捕食者活动的更广泛季节性变化中。我用人工猎物进行了捕食实验，以确定潜在的信号限制（特别是大小和季节）如何塑造捕食风险，进而影响毛虫幼虫个体发育颜色变化的表达。从季节性来看，从7月到9月，捕食和背景绿色度均显著下降，不过几乎没有证据表明这些模式会影响任何一种颜色策略的有效性。毛虫的大小和颜色强烈影响鸟类捕食者的攻击率：无论颜色如何，攻击率都随猎物大小的增加而增加，总体而言，有眼斑的猎物比伪装的猎物更容易受到攻击。这些结果可能反映了有眼斑猎物在显眼性和威慑力之间关键的大小介导权衡，并引发了关于行为和信号环境的相互交织方面如何在自然界中维持大型有眼斑幼虫普遍存在的问题。
