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）可帮助生物体应对当前环境的波动，包括温度变化，但并非所有环境的变异程度均一致。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。在此情况下，表型可塑性或完全丧失，或通过维持原有或改变后的反应规范（reaction norm）得以保留，具体取决于可塑性的成本等因素。本研究以马兜铃凤蝶幼虫（Battus philenor）为实验材料，在该物种美国本土的分布范围内开展调查，检测了两种避热表型可塑性——体色变化与避热栖所搜寻行为——的差异；其中分布区东部气候较为凉爽，此前未观察到体色变化现象，且该性状无表达必要。研究结果显示，所有被调查种群均保留了避热行为与体色变化两种可塑性性状。具体而言，体色变化的反应规范几乎未发生改变，而避热栖所搜寻的阈值在不同种群间仅存在微小差异。上述结果表明，这些可塑性性状的成本足够低，足以通过种群间微弱的基因流维持其存在。本研究证实，在无需表达可塑性的种群中，该性状仍可保持不变并持续存在；同时讨论了这种可塑性保留对表型可塑性的生态学与进化研究的潜在影响。