Data from: Adaptive developmental plasticity in a butterfly: mechanisms for size and time at pupation differ between diapause and direct development

Diapause (overwintering) and direct development are alternative developmental pathways in temperate insects. Diapause necessitates physiological preparations for dormancy, while direct development is associated with strong time constraints, resulting in selection for fast development under the direct development pathway. Physiological and behavioural preparations for pupation contribute to development time, so divergent selection in them is expected between the alternative developmental pathways. Critical mass for pupation induction is a central physiological parameter for the pupation process. Here, we compare the critical masses and the characteristics of the wandering stage – wandering taking place after the cessation of growth and before pupation – between diapausing and directly developing larvae in the butterfly Pieris napi. Critical mass estimation succeeded only for diapausing individuals, among which it was lower in females than in males, indicating an inter-pathway difference in the physiology of critical mass. Directly developing individuals wandered for a shorter time and distance and lost less mass before pupation than diapausing individuals. These physiological and behavioural differences represent adaptive phenotypic plasticity and contribute to fast development under direct development. Thus, the observed developmental plasticity in physiology offers a mechanistic explanation for adaptive life-history variation between alternative developmental pathways and sexual dimorphism.

滞育（Diapause，越冬型）与直接发育是温带昆虫的两种可选发育途径。滞育需要为休眠状态进行生理准备，而直接发育则面临严苛的时间限制，因此直接发育路径下的类群会受到快速发育的选择压力。化蛹的生理与行为准备会影响发育时长，因此两种备选发育路径间，这类准备会受到差异化的选择作用。化蛹诱导临界体重（Critical mass）是化蛹过程的核心生理参数。本研究以绿脉菜粉蝶（Pieris napi）为实验对象，对比了滞育型与直接发育型幼虫的化蛹临界体重，以及徘徊期（Wandering stage，即生长停止后、化蛹前的移动阶段）的特征。仅在滞育型个体中成功测得化蛹临界体重，且滞育型雌虫的临界体重低于雄虫，这表明不同发育路径间的临界体重生理机制存在差异。与滞育型个体相比，直接发育型个体的徘徊时长更短、移动距离更短，且化蛹前的体重流失量更少。这些生理与行为差异属于适应性表型可塑性，且有助于直接发育路径下的快速发育。因此，本研究观测到的生理发育可塑性，为不同备选发育路径间的适应性生活史变异以及性二态性提供了机制层面的解释。