Department of Genetics and Odum School of Ecology, University of Georgia, Athens, Georgia, 30602.
Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, New York, 14850.
Evolution. 2021 Jul;75(7):1711-1726. doi: 10.1111/evo.14280. Epub 2021 Jun 19.
Spatial and temporal environmental variation can favor the evolution of adaptive phenotypic plasticity, such that genotypes alter their phenotypes in response to local conditions to maintain fitness across heterogeneous landscapes. When individuals show greater fitness in one habitat than another, asymmetric migration can restrict adaptation to the lower quality environment. In these cases, selection is predicted to favor traits that enhance fitness in the higher-quality (source) habitat at the expense of fitness in the marginal (sink) habitat. Here, we test whether plasticity is adaptive in a system regulated by demographic source-sink dynamics. Vaccinium elliottii (Ericaceae) occurs in dry upland and flood-prone bottomland forests throughout the southeastern United States, but has larger populations and higher average individual fitness in upland sites. We conducted a multi-year field experiment to evaluate whether plasticity in foliar morphology increases survival and lifespan. Both across and within habitats, selection favored plasticity in specific leaf area, stomatal density, and leaf size. Stabilizing selection acted on plasticity in stomatal density within habitats, suggesting that extreme levels of plasticity are disadvantageous. Thus, even in systems driven by source-sink dynamics, temporal and spatial variation in conditions across the landscape and within habitat types can favor the evolution of plasticity.
空间和时间上的环境变化可以促进适应性表型可塑性的进化，使得基因型根据当地条件改变表型，从而在异质景观中保持适应性。当个体在一种生境中比另一种生境表现出更大的适应性时，不对称的迁移会限制对低质量环境的适应。在这些情况下，选择预计会有利于增强在高质量（源）生境中适应性的特征，而牺牲在边缘（汇）生境中的适应性。在这里，我们测试了在一个由人口源-汇动态调节的系统中，可塑性是否具有适应性。 Vaccinium elliottii（杜鹃花科）分布在美国东南部的干旱高地和洪水泛滥的低地森林中，但在高地的种群数量更大，个体平均适应性更高。我们进行了一项为期多年的实地实验，以评估叶片形态可塑性是否会增加存活率和寿命。无论是在生境之间还是在生境内部，对特定叶面积、气孔密度和叶片大小的可塑性都有选择作用。生境内部气孔密度的可塑性受到稳定选择的作用，这表明极端水平的可塑性是不利的。因此，即使在源-汇动态驱动的系统中，景观上的时间和空间变化以及生境类型内部的条件变化也可以促进可塑性的进化。
