ABSTRACT

A classic example of phenotypic plasticity in plants is the set of traits that change in response to shade. There is widespread evidence that plants in low light conditions often avoid shade by growing taller or by increasing their photosynthetic efficiency, i.e. the shade avoidance syndrome. Whether this plasticity might evolve in response to natural selection depends upon the presence of its standing genetic variation in wild populations. There is limited evidence for heritable standing variation in the plastic response of plants to shade. In this study, we used an experimental common garden approach to investigate this plastic response in snapdragon plants (Antirrhinum majus L.) originating from four natural populations from the Mediterranean region. Our results showed that individual plants reacted strongly to the presence of shade by growing longer shoots, longer internodes, and increasing their specific leaf area in these four populations. Our results also revealed genetic variation for the plastic response within these populations, as well as little genetic constraints to its evolution. Our findings imply that natural populations of A. majus harbour standing genetic variation for phenotypic plasticity in response to shade, providing them the potential to evolve in response to selection.

摘要

植物表型可塑性的一个典型例子是响应于阴影而变化的一组性状。有广泛的证据表明，弱光条件下的植物通常会通过长高或增加其光合效率来避免遮荫，即避荫综合症。这种可塑性是否会响应自然选择而进化，取决于其在野生种群中是否存在遗传变异。仅有有限的证据表明植物对树荫的可塑性响应存在可遗传的站立变化。在这项研究中，我们使用了常用的实验方法花园调查金鱼草植物这种塑料响应（金鱼草L.）来自地中海地区的四个自然种群。我们的结果表明，在这四个种群中，通过长出更长的芽，更长的节间并增加其比叶面积，单个植物对阴影的存在产生了强烈的反应。我们的研究结果还揭示了这些种群中可塑性反应的遗传变异，以及对其进化的遗传限制很小。我们的研究结果表明，玛氏假单胞菌的自然种群具有对基因表型可塑性的遗传变异，可以应对阴影，为它们的选择提供了进化的潜力。