Induced defences alter the strength and direction of natural selection on reproductive traits in common milkweed

Evolutionary biologists have long sought to understand the ecological processes that generate plant reproductive diversity. Recent evidence indicates that constitutive antiherbivore defences can alter natural selection on reproductive traits, but it is unclear whether induced defences will have the same effect and whether reduced foliar damage in defended plants is the cause of this pattern. In a factorial field experiment using common milkweed, Asclepias syriaca L., we induced plant defences using jasmonic acid (JA) and imposed foliar damage using scissors. We found that JA-induced plants experienced selection for more inflorescences that were smaller in size (fewer flowers), whereas control plants only experienced a trend towards selection for larger inflorescences (more flowers); all effects were independent of foliar damage. Our results demonstrate that induced defences can alter both the strength and direction of selection on reproductive traits, and suggest that antiherbivore defe...进化生物学家长期以来一直致力于阐明驱动植物繁殖多样性产生的生态过程。现有研究证据表明，组成型抗草食动物防御（constitutive antiherbivore defences）可改变繁殖性状的自然选择，但目前尚不清楚诱导型抗草食动物防御是否会产生相同效应，以及被防御植物的叶片损伤减少是否为该规律的成因。本研究以普通马利筋（Asclepias syriaca L.）为材料，通过茉莉酸（jasmonic acid, JA）诱导植物防御，并使用剪刀施加叶片损伤，开展了析因田间试验。研究结果显示，经茉莉酸诱导的植株呈现出对更多小型花序（inflorescences）（即花朵数量更少）的选择倾向，而对照组植株仅表现出对大型花序（花朵数量更多）的选择趋势；所有效应均与叶片损伤无关。本研究结果证实，诱导型防御可改变繁殖性状自然选择的强度与方向，且表明抗草食动物防御...