Variation in Plant Response to Herbivory Underscored by Functional Traits

The effects of herbivory can shape plant communities and evolution. However, the many forms of herbivory costs and the wide variation in herbivory pressure, including across latitudinal gradients, can make predicting the effects of herbivory on different plant species difficult. Functional trait approaches may aid in contextualizing and standardizing the assessment of herbivory impacts. Here we assessed the response of 26 old-field plant species to simulated defoliation in a greenhouse setting by measuring whole plant and leaf level traits in control and treated individuals. Simulated defoliation had no significant effects on any plant traits measured. However, the baseline leaf level traits of healthy plants consistently predicted the log response ratio for these species whole plant response to defoliation. The latitudinal mid-point of species’ distributions was also significantly correlated with aboveground biomass and total leaf area responses, with plants with a more northern distribution being more negatively impacted by treatment. These results indicate that even in the absence of significant overall impacts, functional traits may aid in predicting variability in plant responses to defoliation and in identifying the underlying limitations driving those responses.

植食作用（herbivory）的效应可塑造植物群落结构与演化进程。然而，植食作用存在多种成本类型，且植食压力存在广泛差异——包括沿纬度梯度的变化——这使得预测植食作用对不同植物物种的效应颇具难度。功能性状（functional trait）方法有助于明确植食作用影响的研究背景并统一其评估标准。本研究在温室环境中，通过测定对照组与处理组植株的全株性状及叶片性状，评估了26种弃耕地（old-field）植物物种对模拟去叶（simulated defoliation）的响应。结果显示，模拟去叶对本次测定的所有植物性状均无显著影响。不过，健康植株的基准叶片性状可稳定预测各物种全株对去叶处理的对数响应比（log response ratio）。物种分布的纬度中点也与地上生物量及总叶面积的响应显著相关：分布纬度更偏北的植株受处理的负面影响更为显著。本研究结果表明，即便整体效应未达显著水平，功能性状方法仍有助于预测植物对去叶的响应差异，并可明确驱动这些响应的内在限制因素。