Museum of Vertebrate Zoology, University of California, Berkeley, 3101 Valley Life Sciences Building, Berkeley, CA 94720, USA; Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, Santa Cruz, CA 95064, USA.
Museum of Vertebrate Zoology, University of California, Berkeley, 3101 Valley Life Sciences Building, Berkeley, CA 94720, USA; Computational Genomics Resource Laboratory (CGRL), California Institute for Quantitative Biosciences (QB3), University of California, Berkeley, Berkeley, CA 94720, USA.
Curr Biol. 2018 Sep 24;28(18):2970-2977.e7. doi: 10.1016/j.cub.2018.06.075. Epub 2018 Sep 6.
Phenotypic plasticity has been hypothesized to precede and facilitate adaptation to novel environments [1-8], but examples of plasticity preceding adaptation in wild populations are rare (but see [9, 10]). We studied a population of side-blotched lizards, Uta stansburiana, living on a lava flow that formed 22,500 years ago [11] to understand the origin of their novel melanic phenotype that makes them cryptic on the black lava. We found that lizards living on and off of the lava flow exhibited phenotypic plasticity in coloration but also appeared to have heritable differences in pigmentation. We sequenced the exomes of 104 individuals and identified two known regulators of melanin production, PREP and PRKAR1A, which had markedly increased levels of divergence between lizards living on and off the lava flow. The derived variants in PREP and PRKAR1A were only found in the lava population and were associated with increased pigmentation levels in an experimental cohort of hatchling lizards. Simulations suggest that the derived variants in the PREP and PRKAR1A genes arose recently and were under strong positive selection in the lava population. Overall, our results suggest that ancestral plasticity for coloration facilitated initial survival in the lava environment and was followed by genetic changes that modified the phenotype in the direction of the induced plastic response, possibly through de novo mutations. These observations provide a detailed example supporting the hypothesis that plasticity aids in the initial colonization of a novel habitat, with natural selection subsequently refining the phenotype with genetic adaptations to the new environment. VIDEO ABSTRACT.
表型可塑性被假设为先于并促进对新环境的适应[1-8]，但在野生种群中，表型可塑性先于适应的例子很少见（但参见[9,10]）。我们研究了生活在 22500 年前形成的熔岩流上的侧斑鬣蜥 Uta stansburiana 种群，以了解它们在黑色熔岩上具有隐蔽性的新型黑化表型的起源。我们发现，生活在熔岩流上和远离熔岩流的蜥蜴在颜色上表现出表型可塑性，但似乎在色素沉着方面也存在可遗传的差异。我们对 104 个个体的外显子组进行了测序，鉴定出了两个已知的黑色素生成调节剂 PREP 和 PRKAR1A，它们在生活在熔岩流上和远离熔岩流的蜥蜴之间的分化水平明显增加。PREP 和 PRKAR1A 中的衍生变体仅在熔岩种群中发现，并与孵化蜥蜴实验队列中色素沉着水平的增加相关。模拟表明，PREP 和 PRKAR1A 基因中的衍生变体最近才出现，并在熔岩种群中受到强烈的正选择。总体而言，我们的研究结果表明，颜色的祖先可塑性促进了在熔岩环境中的最初生存，随后发生了遗传变化，使表型朝着诱导的可塑性反应方向发生改变，可能是通过新的突变。这些观察结果提供了一个详细的例子，支持了这样一种假说，即可塑性有助于初始定居新栖息地，随后自然选择通过对新环境的遗传适应来进一步完善表型。视频摘要。
