Cisternas Mónica F, Ríos Rodrigo S, Gianoli Ernesto
Departamento de Biología, Universidad de La Serena, La Serena, Chile.
Department of Biological Sciences, Tarleton State University, Stephenville, TX, 76402, USA.
Naturwissenschaften. 2025 Sep 25;112(5):73. doi: 10.1007/s00114-025-02027-6.
Group living in gregarious caterpillars provides several benefits, including enhanced anti-predator defense and improved thermoregulation. Melanism affects both thermoregulation, with melanic forms warming up faster, and anti-predator protection, through its link to aposematic coloration and cuticle thickening. Due to the macroevolutionary association between larval gregariousness and aposematic coloration in Lepidoptera, it has been hypothesized that gregariousness could have evolved to maximize the warning coloration signal. We evaluated melanism patterns in caterpillars from the gregarious swallowtail Battus polydamas archidamas reared singly and in groups of ten individuals. We compared melanism in caterpillars from two populations differing in climate and predation risk, testing for an association between melanism and thermoregulation and/or anti-predator protection. We expected to find darker caterpillars in the colder population, which also showed a higher predation risk from ants. Considering that the group of caterpillars may maximize the warning signal, we hypothesized that solitary caterpillars would be darker (more aposematic). The degree of larval melanism was similar in both populations. Caterpillars in groups showed decreased levels of melanism compared to solitary caterpillars in both populations. Concerning performance costs of melanism, darker caterpillars were slightly-yet not significantly-smaller. Results suggest that the patterns of larval melanism in solitary vs gregarious caterpillars might be rather fixed, less related to current ecological conditions than to the evolutionary importance of aposematic coloration. If the general pattern for gregarious caterpillars results to be that larval melanism has negligible costs, then decreased melanism could be considered another benefit of gregariousness in Lepidoptera.
群居毛虫的群体生活带来了诸多益处，包括增强的反捕食防御能力和改善的体温调节能力。黑化现象既影响体温调节，黑化形态的毛虫升温更快，又通过与警戒色和表皮增厚的联系影响反捕食保护。由于鳞翅目幼虫群居性与警戒色之间的宏观进化关联，有人推测群居性可能已经进化以最大化警戒色信号。我们评估了单独饲养和以十只为一组饲养的群居燕尾凤蝶Battus polydamas archidamas毛虫的黑化模式。我们比较了来自两个气候和捕食风险不同的种群的毛虫的黑化情况，测试黑化与体温调节和/或反捕食保护之间的关联。我们预计在较寒冷的种群中会发现颜色更深的毛虫，该种群也显示出来自蚂蚁的更高捕食风险。考虑到毛虫群体可能会最大化警戒信号，我们假设单独的毛虫会颜色更深（更具警戒性）。两个种群中幼虫的黑化程度相似。与两个种群中的单独毛虫相比，群居毛虫的黑化水平降低。关于黑化的性能成本，颜色更深的毛虫略小——但不显著。结果表明，单独与群居毛虫的幼虫黑化模式可能相当固定，与其说是与当前的生态条件相关，不如说是与警戒色的进化重要性相关。如果群居毛虫的一般模式结果是幼虫黑化成本可忽略不计，那么黑化程度降低可被视为鳞翅目群居性的另一个益处。
