Department of Biology, University of Louisville, Louisville, Kentucky, 40292, USA.
Geographical Ecology Group, Department of Biology, University of Oklahoma, Norman, Oklahoma, 73019, USA.
Ecology. 2020 Jun;101(6):e03051. doi: 10.1002/ecy.3051. Epub 2020 Apr 30.
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 critical thermal maximum (CT ) 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 CT in September. The invasive fire ant, Solenopsis invicta, was among the thermally plastic species, but the native thermal specialists still maintained higher CT 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.
昆虫耐热性分析通常表明该特性相对不变，这导致在预测未来物种在变暖世界中的分布时，模型中使用固定的热极值。季节性环境使种群面临广泛的年温度变化。为了评估热极值不变的简化假设，我们在三个季节量化了 26 种蚂蚁物种的耐热性，这三个季节的平均温度相差两倍。我们的最终目标是检验耐热性与每月温度相关的假设。在夏季末（9 月）进行测试的蚂蚁觅食者的平均临界热极值（CTmax）比 3 月和 12 月的要高。在五个季节性通才中，有 4 种在所有三个焦点月份都积极觅食的物种，其 CTmax 平均高 6°C。入侵红火蚁 Solenopsis invicta 是热可塑性物种之一，但本地耐热专业物种的 CTmax 仍高于 S. invicta。我们的研究表明，耐热性可以具有可塑性，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，但也可能为具有固定特性的物种提供竞争优势，并促进对气候变化的恢复力。
