Data from: Sand lizard (Lacerta agilis) phenology in a warming world

Background. Present-day climate change has altered the phenology (the timing of periodic life cycle events) of many plant and animal populations worldwide. Some of these changes have been adaptive, leading to an increase in population fitness, whereas others have been associated with fitness decline. Representing short-term responses to an altered weather regime, hitherto observed changes are largely explained by phenotypic plasticity. However, to track climatically induced shifts in optimal phenotype as climate change proceeds, evolutionary capacity in key limiting climate- and fitness-related traits is likely to be crucial. In order to produce realistic predictions about the effects of climate change on species and populations, a main target for conservation biologists is thus to assess the potential of natural populations to respond by these two mechanisms. In this study we use a large 15-year dataset on an ectotherm model, the Swedish sand lizard (Lacerta agilis), to investigate how higher spring temperature is likely to affect oviposition timing in a high latitude population, a trait strongly linked to offspring fitness and survival. Results.With an interest in both the short- and potential long-term effect of rising temperatures, we applied a random regression model, which yields estimates of population-level plasticity and among-individual variation in the average, as well as the plastic, response to temperature. Population plasticity represents capacity for short-term adjustments whereas variation among individuals in a fitness-related trait indicates an opportunity for natural selection and hence for evolutionary adaptation. The analysis revealed both population-level plasticity and individual-level variation in average laying date. In contrast, we found no evidence for variation among females in their plastic responses to spring temperature, which could demonstrate a similarity in responses amongst females, but may also be due to a lack of statistical power to detect such an effect. Conclusion. Our findings indicate that climate warming may have positive fitness effects in this lizard population through an advancement of oviposition date. This prediction is consistent over shorter and potentially also longer time scales as the analysis revealed both population-level plasticity and individual-level variation in average laying date. However, the genetic basis for this variation would have to be examined in order to predict an evolutionary response.背景：当前的气候变化已改变了全球范围内诸多动植物种群的物候学（phenology，即周期性生命活动事件的发生时间）。其中部分变化具有适应性，可提升种群适合度（fitness）；另有一些变化则与适合度下降相关。迄今为止观测到的此类变化多为对天气格局改变的短期响应，大多可通过表型可塑性（phenotypic plasticity）得到解释。然而，随着气候变化持续推进，若要追踪气候诱导的最优表型偏移，关键的限制性气候相关性状与适合度相关性状的演化能力或至关重要。为了对气候变化给物种及种群带来的影响做出切合实际的预测，保护生物学家的核心目标之一便是评估自然种群通过这两种机制做出响应的潜力。本研究依托一项针对变温动物（ectotherm）模式物种——瑞典沙蜥（Lacerta agilis）的长达15年的大型数据集，探究春季升温可能对高纬度种群的产卵时间（oviposition timing）产生何种影响——该性状与后代适合度及存活率紧密相关。 结果：鉴于我们同时关注升温的短期效应与潜在长期效应，本研究采用了随机回归模型（random regression model），该模型可估算种群水平的可塑性，以及个体在平均性状表现与温度可塑性响应上的变异。种群可塑性代表了种群进行短期调整的能力，而适合度相关性状的个体间变异则为自然选择提供了空间，进而为演化适应创造了条件。分析结果显示，产卵平均日期同时存在种群水平的可塑性与个体间变异。与之相反，我们未发现雌性个体在春季温度的可塑性响应上存在变异的证据：这既可能表明雌性个体间的响应具有高度相似性，但也可能是由于检测该效应的统计效力（statistical power）不足所致。 结论：我们的研究结果表明，气候变暖或可通过提前产卵日期，提升该蜥蜴种群的适合度。鉴于分析结果同时揭示了种群水平的可塑性与产卵平均日期的个体间变异，这一预测在短期以及潜在的长期时间尺度上均成立。不过，若要预测该种群的演化响应，仍需对该性状变异的遗传基础展开进一步研究。