Data from: No geographic variation in thermoregulatory color plasticity and limited variation in heat-avoidance behavior in Battus philenor caterpillars

Phenotypic plasticity can help organisms cope with variation in their current environment, including temperature variation, but not all environments are equally variable. In the least variable or extreme environments, plasticity may no longer be used. In this case, the plasticity could be lost all together, or it could persist with either the same or an altered reaction norm, depending on factors such as the plasticity's costs. In the pipevine swallowtail caterpillar (Battus philenor), I tested for changes in two forms of heat-avoidance plasticity, color change and refuge-seeking behavior, across the species’ range in the United states, including the cooler eastern parts of its range where color change has not been observed and is unlikely to be needed. I found that both heat-avoidance behavior and color change persisted in all surveyed populations. Indeed, the reaction norm for color change remained nearly unaltered, while the threshold for refuge-seeking only changed slightly across populations. These results suggest that the costs of these plastic traits are low enough for them to be maintained by whatever minimal gene flow the population receives. I show that plasticity can be maintained unaltered in populations where it is not used and discuss the potential consequences of this persistence for both the ecology and evolution of plasticity.

表型可塑性（phenotypic plasticity）可帮助生物应对当前所处环境的变化，包括温度波动，但并非所有环境的变异程度都一致。在变异程度最低或极端的环境中，表型可塑性可能不再被启用。此时，可塑性或完全丧失，或仍以原有或改变后的反应规范（reaction norm）持续存在，这取决于可塑性成本等相关因素。
在马兜铃凤蝶幼虫（Battus philenor，pipevine swallowtail caterpillar）中，本研究针对该物种在美国境内的分布范围，检测了两种避热可塑性——体色变化与避难行为——的变化情况，其中包括其分布范围内较为凉爽的东部区域，该区域此前未观察到体色变化现象，且体色变化不太可能被需要。
研究发现，在所调查的所有种群中，避热行为与体色变化均持续存在。事实上，体色变化的反应规范几乎未发生改变，而避难行为的阈值仅在不同种群间存在小幅变化。上述结果表明，这些可塑性性状的成本足够低，足以通过种群接收的最低限度基因流维持其存续。
本研究证实，在无需使用可塑性的种群中，可塑性仍可保持不变，并讨论了这种持续存在对可塑性生态学与进化研究的潜在影响。