Abstract

To accurately predict species’ phenology under climate change, we need to gain a detailed mechanistic understanding of how different environmental cues interact to produce the seasonal timing response. In the winter moth (Operophtera brumata), seasonal timing of egg hatching is strongly affected by ambient temperature and has been under strong climate change-induced selection over the past 25 years. However, it is unclear whether photoperiod received at the egg stage also influences timing of egg hatching. Here, we investigated the relative contribution of photoperiod and temperature in regulating winter moth egg development using two split-brood experiments. We experimentally shifted the photoperiod eggs received by 2–4 weeks compared to the actual calendar date and measured the timing of egg hatching, both at a constant temperature and in combination with two naturally changing temperature treatments – mimicking a cold and a warm year. We found an eight-fold larger effect of temperature compared to photoperiod on egg development time. Moreover, the very small photoperiod effects we found were outweighed by both between- and within-clutch variation in egg development time. Thus, we conclude that photoperiod received at the egg stage does likely not play a substantial role in regulating the seasonal timing of egg hatching in the winter moth. These insights into the regulatory mechanism of seasonal timing could have important implications for predicting insect climate change adaptation, as we might expect different targets of selection depending on the relative contribution of different environmental cues.

中文翻译：

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与光周期相比，温度在调节冬蛾卵孵化的季节时间方面起着压倒性的作用

摘要

为了准确预测气候变化下物种的物候，我们需要详细了解不同环境因素如何相互作用以产生季节性时间响应。对于冬蛾 ( Operophtera brumata )，卵孵化的季节性时间受到环境温度的强烈影响，并且在过去 25 年中一直受到气候变化引起的强烈选择。然而，尚不清楚卵阶段接受的光周期是否也会影响卵孵化的时间。在这里，我们通过两个分巢实验研究了光周期和温度在调节冬蛾卵发育中的相对贡献。我们通过实验将收到的光周期鸡蛋与实际日历日期相比移动了 2-4 周，并在恒温和结合两种自然变化的温度处理（模拟寒冷和温暖的年份）的情况下测量了鸡蛋的孵化时间。我们发现温度对卵子发育时间的影响比光周期大八倍。此外，我们发现的非常小的光周期效应被卵子发育时间的卵间和卵内变化所抵消。因此，我们得出的结论是，卵阶段接受的光周期在调节冬蛾卵孵化的季节性时间方面可能不会发挥实质性作用。这些对季节时间调节机制的见解可能对预测昆虫气候变化适应具有重要意义，因为我们可能会根据不同环境因素的相对贡献来预期不同的选择目标。