Department of Systematic Zoology, Adam Mickiewicz University of Poznan, Poznań, Poland.
Emerging Pests and Pathogens Research Unit, Robert W. Holley Center for Agriculture and Health, Ithaca, New York, United States.
PeerJ. 2024 Oct 16;12:e18295. doi: 10.7717/peerj.18295. eCollection 2024.
Insects often show adaptive phenotypic plasticity where environmental cues during early stages are used to produce a phenotype that matches the environment experienced by adults. Many tropical satyrine butterflies (Nymphalidae: Satyrinae) are seasonally polyphenic and produce distinct wet- and dry-season form adults, providing tight environment-phenotype matching in seasonal environments. In studied Mycalesina butterflies, dry-season forms can be induced in the laboratory by growing larvae at low temperatures or on poor food quality. Since both these factors also tend to reduce larval growth rate, larval growth rate may be an internal cue that translates the environmental cues into the expression of phenotypes. If this is the case, we predict that slower-growing larvae would be more likely to develop a dry-season phenotype.
We performed the first experimental study on seasonal polyphenism of a butterfly in the tribe Melanitini. We measured both larval growth rate and adult phenotype (eyespot size and wing shape) of common evening brown butterflies (), reared at various temperatures and on various host-plant species. We constructed provisional reaction norms, and tested the hypothesis that growth rate mediates between external cues and adult phenotype.
Reaction norms were similar to those found in Mycalesina butterflies. We found that both among and within treatments, larvae with lower growth rates (low temperature, particular host plants) were more likely to develop dry-season phenotypes (small eyespots, falcate wing tips). However, among temperature treatments, similar growth rates could lead to very different wing phenotypes, and within treatments the relationships were weak. Moreover, males and females responded differently, and eyespot size and wing shape were not strongly correlated with each other. Overall, larval growth rate seems to be weakly related to eyespot size and wing shape, indicating that seasonal plasticity in is primarily mediated by other mechanisms.
昆虫经常表现出适应性表型可塑性，即在早期阶段，环境线索被用来产生一种与成虫经历的环境相匹配的表型。许多热带 satyrine 蝴蝶（鳞翅目：Satyrinae）具有季节性多态性，产生明显的湿季和干季成虫形式，在季节性环境中实现了紧密的环境-表型匹配。在所研究的 Mycalesina 蝴蝶中，干季形式可以通过在低温下或在低质量的食物上饲养幼虫在实验室中诱导产生。由于这两个因素也往往会降低幼虫的生长速度，因此幼虫的生长速度可能是一个内部线索，将环境线索转化为表型的表达。如果是这样，我们预测生长速度较慢的幼虫更有可能发育出干季表型。
我们首次对 Melanitini 部落的蝴蝶季节性多态性进行了实验研究。我们测量了常见的傍晚棕色蝴蝶（）的幼虫生长速度和成虫表型（眼斑大小和翅膀形状），这些蝴蝶在不同的温度和不同的寄主植物上饲养。我们构建了暂定的反应规范，并检验了生长速度在外部线索和成虫表型之间起中介作用的假设。
反应规范与 Mycalesina 蝴蝶中发现的相似。我们发现，无论是在处理之间还是在处理内，生长速度较低的幼虫（低温、特定的寄主植物）更有可能发育出干季表型（小眼斑、镰刀状的翅尖）。然而，在温度处理之间，相似的生长速度可能导致非常不同的翅膀表型，而在处理内，这种关系很弱。此外，雄性和雌性的反应不同，眼斑大小和翅膀形状彼此之间相关性不强。总的来说，幼虫生长速度与眼斑大小和翅膀形状的关系较弱，表明 的季节性可塑性主要由其他机制介导。
