Institute of Biology, Leiden University, Leiden, The Netherlands.
Proc Biol Sci. 2011 Mar 7;278(1706):789-97. doi: 10.1098/rspb.2010.1560. Epub 2010 Sep 8.
Polyphenisms-the expression of discrete phenotypic morphs in response to environmental variation-are examples of phenotypic plasticity that may potentially be adaptive in the face of predictable environmental heterogeneity. In the butterfly Bicyclus anynana, we examine the hormonal regulation of phenotypic plasticity that involves divergent developmental trajectories into distinct adult morphs for a suite of traits as an adaptation to contrasting seasonal environments. This polyphenism is induced by temperature during development and mediated by ecdysteroid hormones. We reared larvae at separate temperatures spanning the natural range of seasonal environments and measured reaction norms for ecdysteroids, juvenile hormones (JHs) and adult fitness traits. Timing of peak ecdysteroid, but not JH titres, showed a binary response to the linear temperature gradient. Several adult traits (e.g. relative abdomen mass) responded in a similar, dimorphic manner, while others (e.g. wing pattern) showed a linear response. This study demonstrates that hormone dynamics can translate a linear environmental gradient into a discrete signal and, thus, that polyphenic differences between adult morphs can already be programmed at the stage of hormone signalling during development. The range of phenotypic responses observed within the suite of traits indicates both shared regulation and independent, trait-specific sensitivity to the hormone signal.
多态现象——即对环境变化表现出离散表型形态的现象——是表型可塑性的一个例子，这种可塑性在面对可预测的环境异质性时可能具有适应性。在蝴蝶 Bicyclus anynana 中，我们研究了涉及到不同发育轨迹的表型可塑性的激素调节，这些不同的发育轨迹导致了一系列特征的不同成年形态，这是对对比鲜明的季节性环境的一种适应。这种多态性是由发育过程中的温度诱导的，并由蜕皮激素调节。我们在跨越季节性环境自然范围的不同温度下饲养幼虫，并测量了蜕皮激素、保幼激素 (JH) 和成虫适应性特征的反应规范。蜕皮激素的峰值时间而不是 JH 滴度表现出对线性温度梯度的二元反应。一些成年特征（例如相对腹部质量）以类似的二态方式响应，而其他特征（例如翅膀图案）则呈线性响应。这项研究表明，激素动态可以将线性环境梯度转化为离散信号，因此，在发育过程中的激素信号阶段，成年形态之间的多态差异已经可以被编程。在所研究的特征范围内观察到的表型反应范围表明，对激素信号存在共同的调节和独立的、特征特异性的敏感性。
