Nielsen M E
Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ, USA.
J Evol Biol. 2017 Oct;30(10):1919-1928. doi: 10.1111/jeb.13168. Epub 2017 Sep 7.
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 altogether, 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, colour change and refuge-seeking behaviour, across the species' range in the United states, including the cooler eastern parts of its range where colour change has not been observed and is unlikely to be needed. I found that both heat-avoidance behaviour and colour change persisted in all surveyed populations. Indeed, the reaction norm for colour change remained nearly unaltered, whereas 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.
表型可塑性有助于生物体应对当前环境中的变化，包括温度变化，但并非所有环境的变化程度都相同。在变化最小或极端的环境中，可塑性可能不再被利用。在这种情况下，可塑性可能会完全丧失，或者根据可塑性成本等因素，它可能会以相同或改变的反应规范持续存在。在北美 Pipevine 燕尾蝶幼虫（Battus philenor）中，我测试了在美国该物种分布范围内两种热回避可塑性形式的变化，即颜色变化和寻求避难行为，其分布范围包括较凉爽的东部地区，在该地区未观察到颜色变化且不太可能需要这种变化。我发现，在所有调查的种群中，热回避行为和颜色变化都持续存在。事实上，颜色变化的反应规范几乎没有改变，而寻求避难的阈值在不同种群中仅略有变化。这些结果表明，这些可塑性特征的成本足够低，以至于无论种群接受何种最小程度的基因流动，它们都能得以维持。我表明，可塑性在未被利用的种群中可以保持不变，并讨论了这种持续性对可塑性的生态学和进化的潜在影响。
