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，即越冬休眠）与直接发育（direct development）是温带昆虫（temperate insects）的两类备选发育路径。滞育需要为休眠开展系统性生理准备，而直接发育则受严格的时间约束，因此在直接发育路径下会受到针对快速发育的选择压力。化蛹（pupation）相关的生理与行为准备过程会影响发育时长，故而两类备选发育路径间，这些准备过程预期会受到分化选择。化蛹诱导临界体重（Critical mass for pupation induction）是化蛹过程的核心生理调控参数。本研究以绿脉菜粉蝶（*Pieris napi*）为研究对象，对比滞育型与直接发育型幼虫的临界体重，以及漫游期（wandering stage）的特征——漫游期指生长停止后、化蛹前的阶段。本研究仅在滞育个体中成功测得临界体重，且该群体中雌性的临界体重低于雄性，表明临界体重的生理调控机制在两类发育路径间存在差异。与滞育个体相比，直接发育个体的漫游时长更短、漫游距离更小，且化蛹前的体重流失更少。上述生理与行为差异属于适应性表型可塑性（adaptive phenotypic plasticity），可助力直接发育路径下实现快速发育。综上，本研究观测到的生理发育可塑性，为两类备选发育路径间的适应性生活史变异（life-history variation）以及雌雄二型性（sexual dimorphism）提供了机制层面的解释。