Department of Biology, Utah State University, Logan, UT 84322, USA.
Proc Natl Acad Sci U S A. 2010 Mar 2;107(9):4260-3. doi: 10.1073/pnas.0912748107. Epub 2010 Feb 16.
A central role for phenotypic plasticity in adaptive evolution is often posited yet lacks empirical support. Selection for the stable production of an induced phenotype is hypothesized to modify the regulation of preexisting developmental pathways, producing rapid adaptive change. We examined the role of plasticity in rapid adaptation of the zooplankton Daphnia melanica to novel fish predators. Here we show that plastic up-regulation of the arthropod melanin gene dopa decarboxylase (Ddc) in the absence of UV radiation is associated with reduced pigmentation in D. melanica. Daphnia populations coexisting with recently introduced fish exhibit environmentally invariant up-regulation of Ddc, accompanied by constitutive up-regulation of the interacting arthropod melanin gene ebony. Both changes in regulation are associated with adaptive reduction in the plasticity and mean expression of melanin. Our results provide evidence that the developmental mechanism underlying ancestral plasticity in response to an environmental factor has been repeatedly co-opted to facilitate rapid adaptation to an introduced predator.
表型可塑性在适应性进化中起着核心作用，这一观点经常被提出，但缺乏实证支持。有人假设，为稳定产生诱导表型而进行的选择，会改变预先存在的发育途径的调控，从而产生快速的适应性变化。我们研究了浮游动物黑腹溞（Daphnia melanica）对新型鱼类捕食者快速适应过程中可塑性的作用。在这里，我们表明，在没有紫外线辐射的情况下，昆虫黑色素基因多巴脱羧酶（Ddc）的可塑性上调与黑腹溞色素沉着减少有关。与最近引入的鱼类共存的黑腹溞种群中，Ddc 表现出环境不变的上调，同时与之相互作用的昆虫黑色素基因 ebony 也表现出组成型上调。调控的这两种变化都与黑色素可塑性和平均表达的适应性降低有关。我们的研究结果提供了证据，证明了对环境因素的反应中祖先可塑性的发育机制已被多次采用，以促进对引入捕食者的快速适应。
