Analyses of heat tolerance in insects often suggest that this trait is relatively invariant, leading to the use of fixed thermal maxima in models predicting future distribution of species in a warming world. Seasonal environments expose populations to a wide annual temperature variation. To evaluate the simplifying assumption of invariant thermal maxima, we quantified heat tolerance of 26 ant species across three seasons that vary two-fold in mean temperature. Our ultimate goal was to test the hypothesis that heat tolerance tracks monthly temperature. Ant foragers tested at the end of the summer, in September, had higher average CTmax compared to those in March and December. Four out of five seasonal generalists-species actively foraging in all three focal months-had, on average, 6°C higher CTmax in September. The invasive fire ant, Solenopsis invicta, was among the thermally plastic species, but the native thermal specialists still maintained higher CTmax than S. invicta. Our study shows that heat tolerance can be plastic, and this should be considered when examining species-level adaptations. Moreover, the plasticity of thermal traits, while potentially costly, may also generate a competitive advantage over species with fixed traits and promote resilience to climate change.

中文翻译：

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蚂蚁耐热性的季节性可塑性

对昆虫耐热性的分析通常表明这种特性是相对不变的，导致在模型中使用固定的热最大值来预测未来物种在变暖世界中的分布。季节性环境使人口每年面临广泛的温度变化。为了评估不变热最大值的简化假设，我们量化了平均温度变化两倍的三个季节中 26 种蚂蚁的耐热性。我们的最终目标是检验耐热性跟踪每月温度的假设。与 3 月和 12 月相比，在 9 月夏末测试的蚂蚁觅食者的平均 CTmax 更高。五分之四的季节性通才——在所有三个重点月份都积极觅食的物种——在 9 月份的 CTmax 平均高出 6°C。入侵的火蚁，Solenopsis invicta 是热塑性物种之一，但本地热专家仍然保持比 S. invicta 更高的 CTmax。我们的研究表明耐热性可以是可塑性的，在检查物种水平的适应性时应该考虑到这一点。此外，热特性的可塑性虽然可能代价高昂，但也可能比具有固定特性的物种产生竞争优势，并促进对气候变化的适应能力。