Data from: Thermal plasticity of growth and development varies adaptively among alternative developmental pathways

Polyphenism, the expression of discrete alternative phenotypes, is often a consequence of a developmental switch. Physiological changes induced by a developmental switch potentially affect reaction norms, but the evolution and existence of alternative reaction norms remains poorly understood. Here, we demonstrate that, in the butterfly Pieris napi (Lepidoptera: Pieridae), thermal reaction norms of several life history traits vary adaptively among switch-induced alternative developmental pathways of diapause and direct development. The switch was affected both by photoperiod and temperature, ambient temperature during late development having the potential to override earlier photoperiodic cues. Directly developing larvae had higher development and growth rates than diapausing ones across the studied thermal gradient. Reaction norm shapes also differed between the alternative developmental pathways, indicating pathway-specific selection on thermal sensitivity. Relative mass increments decreased linearly with increasing temperature and were higher under direct development than diapause. Contrary to predictions, population phenology did not explain trait variation or thermal sensitivity, but our experimental design probably lacks power for finding subtle phenology effects. We demonstrate adaptive differentiation in thermal reaction norms among alternative phenotypes, and suggest that the consequences of an environmentally dependent developmental switch primarily drive the evolution of alternative thermal reaction norms in P. napi.多型现象（Polyphenism）指离散交替表型的表达，通常由发育开关（developmental switch）介导。由发育开关诱导的生理变化或可影响反应规范（reaction norm），但交替反应规范的演化与存在性仍未得到充分阐释。本研究以暗脉菜粉蝶（Pieris napi，鳞翅目：粉蝶科）为对象，结果表明：在滞育（diapause）与直接发育（direct development）这两种由开关诱导的交替发育途径中，多项生活史性状（life history traits）的热反应规范（thermal reaction norms）存在适应性分化。该发育开关同时受光周期（photoperiod）与温度调控，发育后期的环境温度有可能抵消此前的光周期信号。在本次研究覆盖的温度梯度范围内，直接发育幼虫的发育与生长速率均高于滞育幼虫。两种交替发育途径的反应规范形态亦存在差异，表明热敏感性存在途径特异性选择。相对体重增量随温度升高呈线性下降，且直接发育组的相对体重增量高于滞育组。与研究预测相悖的是，种群物候学（phenology）未能解释性状变异或热敏感性差异，推测本实验设计可能不足以检测到微弱的物候学效应。本研究证实了交替表型间热反应规范的适应性分化，并提出：环境依赖性发育开关所带来的效应，是驱动暗脉菜粉蝶交替热反应规范演化的主要驱动因素。