Data from: Photoperiod at the larval stage sets the timing of entire annual program in an herbivorous insect

To maximize their fitness, organisms need to synchronize their phenology with the seasonal variation in environmental conditions. Most phenological traits are affected by environmental abiotic cues such as photoperiod, temperature and rainfall. When individuals with complex life-cycles fail to match one of the stages with the favourable environment, these negative conditions experienced may lead to carry-over effects and, thus, influence fitness in subsequent stages. In the winter moth, an herbivorous insect with an annual life-cycle, timing of egg-hatching in spring is strongly influenced by temperature and varies from year to year. To investigate whether the phenological variation in egg-hatching date affects subsequent stages, we analysed data on egg-hatching and adult catching date (considered here to be a proxy for adult eclosion date) from our long-term study (1994-2014). Furthermore, we experimentally manipulated the photoperiod experienced by newly hatched larvae and recorded the phenology of their subsequent life-cycle stages. In the long-term field study, we found that the timing of winter moth egg-hatching in spring varied strongly from year to year. Interestingly, however, the timing of adult eclosion date in winter showed little inter-annual variation. In line with these findings, our experimental data showed that the winter moth shortened the duration of their pupal development when they experienced a late spring photoperiod as a larva, and prolonged pupal development when experiencing early spring photoperiod conditions. The effects of the larval photoperiodic treatments persisted during egg development in the following generation. The results show that a phenological shift that occurs during an early life-stage is partially compensated during subsequent stages and suggest that the mechanism underlying this compensation is mediated by photoperiod. Winter moths regulated their phenology in such a way that the variation in the egg-hatching stage was not carried over to the next life-cycle stages. This has strong effects on fitness as it (1) ensures the synchronization of adult eclosion during the mating period and (2) is likely to reduce potentially negative fitness consequences of phenological mismatches in egg hatching in the following generation. Overall, these findings stress the importance of understanding phenological carry-over effects to forecast the impact of global change in species with complex life-cycles.为最大化自身适合度（fitness），生物体需将自身物候（phenology）与环境条件的季节波动同步。多数物候性状（phenological traits）受光周期（photoperiod）、温度、降雨等环境非生物线索（abiotic cues）调控。若具有复杂生活史（complex life-cycles）的个体无法让某一生命阶段匹配适宜环境，其所经历的不良环境将引发阶段间遗留效应（carry-over effects），进而对后续阶段的适合度产生影响。 作为具有年生活史（annual life-cycle）的植食性昆虫（herbivorous insect），冬尺蛾（winter moth）春季卵孵化（egg-hatching）时间受温度调控且存在年际差异（inter-annual variation）。为探究卵孵化日期的物候变异是否会影响后续生命阶段，本研究分析了1994-2014年长期监测的卵孵化数据与成虫诱捕日期（本研究中将其作为成虫羽化（adult eclosion）日期的替代指标（proxy））。此外，我们通过实验操控初孵幼虫所经历的光周期，并记录其后续生命阶段的物候变化。 长期野外监测结果显示，冬尺蛾春季卵孵化时间存在显著年际差异。但有趣的是，其冬季成虫羽化时间几乎无年际波动。与该结果一致，实验数据表明：当幼虫经历春季晚光周期时，冬尺蛾会缩短蛹发育（pupal development）时长；而当幼虫经历春季早光周期时，则会延长蛹发育时长。幼虫光周期处理的效应可延续至下一代的卵发育阶段。 研究结果表明，生命早期阶段发生的物候偏移（phenological shift）可在后续阶段得到部分补偿，且该补偿机制由光周期介导。冬尺蛾通过调控自身物候，使卵孵化阶段的变异未传递至后续生命阶段。这一现象对适合度具有显著影响：其一，确保了成虫羽化与交配期同步；其二，可降低下一代卵孵化物候不匹配可能带来的适合度损失。综上，本研究结果凸显了探究物候阶段间遗留效应的重要性，这有助于预测全球变化（global change）对具有复杂生活史物种的影响。