Estimates of lower thermal limits are widely used to infer sensitivity to climate variability, local adaptation and adaptive acclimation responses in ectotherms. These inferences build on the ecological relevance of the tolerance estimates and assume that estimates can be extrapolated to relevant conditions. Methodological effects for upper thermal limits have been extensively investigated, with different ramping rates and acclimation regimes giving rise to varying, and even disparate, conclusions. However, methodological effects have received much less attention for lower thermal limits. In this study, we explicitly test whether methodology could affect estimates of lower thermal limits in interaction with acclimation temperature and thermal variability, by acclimating adult Drosophila melanogaster to different constant and fluctuating temperature regimes and generating reaction norms at different ramping rates. We find that ramping rates have no significant effect on the lower thermal limits. Constant temperature acclimation resulted in non-linear reaction norms, while the introduction of thermal variability during adult life result in linear reaction norms. Thus, applying ecologically relevant conditions (here thermal variability) potentially impacts the results and conclusions of insect low temperature tolerance and acclimation capacity.

下限温度的估计值被广泛用于推断对等温线中气候变化，局部适应和适应性适应性反应的敏感性。这些推论基于公差估计的生态相关性，并假定可以将估计推断到相关条件。对于温度上限的方法学效果已进行了广泛的研究，不同的升温速率和适应方式会得出不同甚至不同的结论。但是，由于较低的热极限，方法学的影响很少受到关注。在这项研究中，我们通过使成年果蝇适应环境，明确测试了方法学是否会影响与适应温度和热变异性相互作用的较低热极限的估计值适应不同的恒定和波动温度范围，并以不同的升温速率生成反应标准。我们发现，升温速率对较低的热极限没有显着影响。恒温驯化导致非线性反应规范，而成年期引入的热变异性导致线性反应规范。因此，应用生态学相关条件（此处为热可变性）可能会影响昆虫低温耐受性和适应能力的结果和结论。