Diapause induction and relaxed selection on alternative developmental pathways in a butterfly

1. Seasonal phenotypic plasticity entails differential trait expression depending on the time of season. The facultative induction of winter diapause in temperate insects is a developmental switch mechanism often leading to differential expression in life history traits. However, when there is a latitudinal shift from a bivoltine to univoltine life cycle, selection for pathway-specific expression is disrupted, which may allow drift towards less optimal trait values within the non-selected pathway. 2. We use field- and experimental data from five Swedish populations of Pararge aegeria to investigate latitudinal variation in voltinism, local adaptation in the diapause switch, and footprints of selection on pathway-specific regulation of life history traits and sexual dimorphism in larval development. 3. Field data clearly illustrated how natural populations gradually shift from bivoltinism to univoltinism as latitude increases. This was supported experimentally as the decrease in direct d...

1. 季节性表型可塑性（seasonal phenotypic plasticity）指生物的性状表达会随季节时序发生差异变化。温带昆虫的冬季滞育（winter diapause）兼性诱导是一种发育开关机制，常引发生活史性状的差异表达。然而，当生活周期从一年两代（bivoltine）向一年一代（univoltine）随纬度梯度转变时，通路特异性表达的选择压力会被打破，这可能导致未受选择的通路朝着性状表现更劣的方向发生遗传漂变。2. 本研究利用来自瑞典5个斑眼蝶（Pararge aegeria）种群的野外与实验数据，探究了其化性随纬度的变异、滞育开关的本地适应性，以及生活史性状通路特异性调控与幼虫发育过程中性二态性（sexual dimorphism）的选择印记。3. 野外数据清晰表明，随着纬度升高，自然种群的化性会逐步从一年两代转变为一年一代。该结果得到了实验验证：直接发育的……