Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853, USA.
New Phytol. 2010 Nov;188(3):856-67. doi: 10.1111/j.1469-8137.2010.03404.x.
• Species that exhibit adaptive plasticity alter their phenotypes in response to environmental conditions, thereby maximizing fitness in heterogeneous landscapes. However, under demographic source-sink dynamics, selection should favor traits that enhance fitness in the source habitat at the expense of fitness in the marginal habitat. Consistent with source-sink dynamics, the perennial blueberry, Vaccinium elliottii (Ericaceae), shows substantially higher fitness and population sizes in dry upland forests than in flood-prone bottomland forests, and asymmetrical gene flow occurs from upland populations into bottomland populations. Here, we examined whether this species expresses plasticity to these distinct environments despite source-sink dynamics. • We assessed phenotypic responses to a complex environmental gradient in the field and to water stress in the glasshouse. • Contrary to expectations, V. elliottii exhibited a high degree of plasticity in foliar and root traits (specific leaf area, carbon isotope ratios, foliar nitrogen content, root : shoot ratio, root porosity and root architecture). • We propose that plasticity can be maintained in source-sink systems if it is favored within the source habitat and/or a phylogenetic artifact that is not costly. Additionally, plasticity could be advantageous if habitat-based differences in fitness result from incipient niche expansion. Our results illuminate the importance of evaluating phenotypic traits and fitness components across heterogeneous landscapes.
• 表现出适应性可塑性的物种会根据环境条件改变其表型，从而在异质景观中最大限度地提高适应性。然而，在种群源汇动态下，选择应该有利于在源生境中提高适应性的特征，而牺牲在边缘生境中的适应性。与源汇动态一致，多年生蓝莓 Vaccinium elliottii（杜鹃花科）在旱地森林中的适应性和种群规模明显高于洪泛区森林，并且从旱地种群到洪泛区种群的基因流是不对称的。在这里，我们研究了尽管存在源汇动态，但该物种是否对这些不同的环境表现出可塑性。 • 我们评估了野外复杂环境梯度和温室水分胁迫下的表型响应。 • 与预期相反，V. elliottii 在叶片和根系特征（比叶面积、碳同位素比、叶片氮含量、根/梢比、根孔隙率和根系结构）方面表现出高度的可塑性。 • 我们提出，如果可塑性在源生境中受到青睐，或者如果它是一个不昂贵的系统进化产物，那么它可以在源汇系统中得到维持。此外，如果基于栖息地的适应性差异是由新生生态位扩张引起的，那么可塑性可能是有利的。我们的研究结果阐明了在异质景观中评估表型特征和适应性成分的重要性。
