Physiological processes vary widely across individuals and can influence how individuals respond to environmental change. Repeatability in how metabolic rate changes across temperatures (i.e. metabolic thermal plasticity) can influence mass-scaling exponents in different thermal environments. Moreover, repeatable plastic responses are necessary for reaction norms to respond to selective forces which is important for populations living in fluctuating environments. Nonetheless, only a small number of studies have explicitly quantified repeatability in metabolic plasticity, and fewer have explored how it can impact mass-scaling. We repeatedly measured standard metabolic rate of n = 42 delicate skinks Lampropholis delicata at six temperatures over the course of four months (N_{[observations]} = 4952). Using hierarchical statistical techniques, we accounted for multi-level variation and measurement error in our data in order to obtain more precise estimates of reaction norm repeatability and mass-scaling exponents at different acute temperatures. Our results show that individual differences in metabolic thermal plasticity were somewhat consistent over time (R_slope = 0.25, 95% CI = 2.48 × 10⁻⁸ – 0.67), however estimates were associated with a large degree of error. After accounting for measurement error, which decreased steadily with temperature, we show that among individual variance remained consistent across all temperatures. Congruently, temperature specific repeatability of average metabolic rate was stable across temperatures. Cross-temperature correlations were positive but were not uniform across the reaction norm. After taking into account multiple sources of variation, our estimates for mass-scaling did not change with temperature and were in line with published values for snakes and lizards. This implies that repeatable plastic responses may promote thermal stability of scaling exponents. Our work contributes to understanding how energy expenditure scales with abiotic and biotic factors and the capacity for reaction norms to respond to selection.

中文翻译：

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热塑性的个体差异及其对质量缩放的影响

生理过程因人而异，并且会影响个人对环境变化的反应。代谢率如何随温度变化的可重复性（即代谢热可塑性）可以影响不同热环境中的质量缩放指数。此外，可重复的塑性反应对于反应规范对选择性力做出反应是必要的，这对于生活在波动环境中的人群很重要。尽管如此，只有少数研究明确量化了代谢可塑性的可重复性，很少有人探索它如何影响质量缩放。我们在四个月的时间里反复测量了 n = 42 个精致的石龙子在六个温度下的标准代谢率( N_[观察]  = 4952）。使用分层统计技术，我们考虑了数据中的多级变异和测量误差，以便更精确地估计不同急性温度下的反应范数可重复性和质量标度指数。我们的结果表明，代谢热可塑性的个体差异随着时间的推移有些一致（R_斜率 = 0.25，95% CI = 2.48 × 10 ^-8– 0.67），但是估计值与很大程度的误差有关。在考虑了随温度稳定下降的测量误差后，我们表明个体差异在所有温度下保持一致。一致地，平均代谢率的温度特异性可重复性在不同温度下是稳定的。跨温度相关性呈正相关，但在整个反应规范中并不统一。在考虑了多种变异来源后，我们对质量尺度的估计不会随温度变化，并且与已公布的蛇和蜥蜴值一致。这意味着可重复的塑性响应可以促进缩放指数的热稳定性。