Intraspecific variation in plant traits is a major cause of variation in herbivore feeding and performance. Plant defensive traits change as a plant grows, such that ontogeny may account for a substantial portion of intraspecific trait variation. We tested how the ontogenic stage of an individual plant, of an individual in the context of its neighboring plants, and of a patch of plants with mixed or uniform stages affect plant–herbivore interactions. To do this, we conducted an experimental study of the interactions between Lepidium draba, a perennial brassicaceous weed, and Plutella xylostella, a common herbivore of L. draba. We found that L. draba foliar glucosinolates, secondary metabolites often implicated in defense, decreased in concentration with plant age. In single-stage patches, herbivores performed similarly on L. draba plants of different ages. Furthermore, we found no difference in the cumulative performance of herbivores reared on mixed- or even-staged patches of L. draba. However, in mixed-stage patches, the damage experienced by a focal plant depended on the stage of neighboring plants, suggesting a preference hierarchy of the herbivore among plant stages. In our study, the amount of herbivory depended on the ontogenic neighborhood in which the plant grew. However, from the herbivore’s perspective, variation in plant ontogenic stage was unimportant to its success in terms of feeding rate and final weight.

植物性状的种内变异是草食动物摄食和繁殖行为变异的主要原因。植物防御性状随着植物的生长而变化，因此个体发育可能占种内性状变异的很大一部分。我们测试了单个植物，一个个体在其邻近植物的环境中以及一个具有混合或统一阶段的植物的个体的个体发育阶段如何影响植物—草食动物的相互作用。为此，我们对多年生的芸苔科杂草Lepidium draba和L. draba的常见草食动物小菜蛾Plutella xylostella之间的相互作用进行了实验研究。我们发现德拉巴叶芥子油苷，次生代谢产物常与防御有关，随着植物年龄的增长其浓度降低。在单阶段补丁中，食草动物在不同年龄的德拉巴草上的表现相似。此外，我们发现在混合或均匀分期的L. draba上饲养的草食动物的累积性能没有差异。然而，在混合阶段的斑块中，局地植物遭受的损害取决于邻近植物的阶段，这表明草食动物在植物阶段之间的偏好等级。在我们的研究中，草食动物的数量取决于植物生长的本体附近。然而，从草食动物的角度来看，植物成虫阶段的变化对其取食速度和最终重量的成功并不重要。