Chemical defences in animals are both incredibly widespread and highly diverse. Yet despite the important role they play in mediating interactions between predators and prey, extensive differences in the amounts and types of chemical compounds can exist between individuals, even within species and populations. Here we investigate the potential role of environment and development on the chemical defences of warningly coloured butterfly species from the tribe Heliconiini, which can both synthesize and sequester cyanogenic glycosides (CGs). We reared 5 Heliconiini species in captivity, each on a single species-specific host plant as larvae, and compared them to individuals collected in the wild to ascertain whether the variation in CG content observed in the field might be the result of differences in host plant availability. Three of these species were reared as larvae on the same host plant, Passiflora riparia, to further test how species, sex, and age affected the type and amount of different defensive CGs, and how they affected the ratio of synthesized to sequestered compounds. Then, focusing on the generalist species Heliconius numata, we specifically explored variation in chemical profiles as a result of the host plant consumed by caterpillars and their brood line, using rearing experiments carried out on two naturally co-occurring host plants with differing CG profiles. Our results show significant differences in both the amount of synthesized and sequestered compounds between butterflies reared in captivity and those collected in the field. We also found a significant effect of species and an effect of sex in some, but not all, species. We show that chemical defences in H. numata continue to increase throughout their life, likely because of continued biosynthesis, and we suggest that variation in the amount of synthesized CGs in this species does not appear to stem from larval host plants, although this warrants further study. Interestingly, we detected a significant effect of brood lines, consistent with heritability influencing CG concentrations in H. numata. Altogether, our results point to multiple factors resulting in chemical defence variation in Heliconiini butterflies and highlight the overlooked effect of synthesis capabilities, which may be genetically determined to some extent.

动物的化学防御非常普遍且高度多样化。然而，尽管它们在调解捕食者和猎物之间的相互作用方面发挥着重要作用，但个体之间，甚至在物种和种群内，化合物的数量和类型可能存在巨大差异。在这里，我们研究了环境和发展对 Heliconiini 部落的警告色蝴蝶物种的化学防御的潜在作用，这些蝴蝶可以合成和隔离氰苷 (CG)。我们圈养了 5 个 Heliconiini 物种，每个物种在作为幼虫的单一物种特异性寄主植物上饲养，并将它们与在野外收集的个体进行比较，以确定在野外观察到的 CG 含量的变化是否可能是寄主植物差异的结果可用性。Passiflora riparia，以进一步测试物种、性别和年龄如何影响不同防御性 CG 的类型和数量，以及它们如何影响合成化合物与隔离化合物的比例。然后，我们专注于通才物种Heliconius numata，使用对具有不同 CG 特征的两种自然共生寄主植物进行的饲养实验，专门探索了化学特征的变化，这是由毛虫及其亲本消耗的寄主植物造成的。我们的研究结果表明，人工饲养的蝴蝶与野外采集的蝴蝶在合成和螯合化合物的数量上存在显着差异。我们还发现物种的显着影响和性别对某些（但不是全部）物种的影响。我们表明化学防御在H. numata在其整个生命周期中继续增加，可能是因为持续的生物合成，我们认为该物种中合成 CG 数量的变化似乎并非源于幼虫寄主植物，尽管这值得进一步研究。有趣的是，我们检测到育种系的显着影响，这与影响H. numata 中CG 浓度的遗传力一致。总而言之，我们的结果指出了导致 Heliconiini 蝴蝶化学防御变异的多种因素，并强调了合成能力的被忽视的影响，这可能在某种程度上是由基因决定的。