Data from: Costs of resistance and correlational selection in the multiple-herbivore community of Solanum carolinense

Although a central assumption of most plant-defense theories is that resistance is costly, fitness costs have proven difficult to detect in the field. One useful, though labor-intensive, method to detect costs is to quantify stabilizing selection acting on resistance in field populations. Here, we report on an experimental field study of Solanum carolinense in which we employed a quadratic phenotypic-selection analysis on 12 types of resistance (defined operationally as one minus the proportion of tissue damaged) involving nine species of herbivores. For seven types of resistance, we found significant stabilizing selection and intermediate optimum levels, indicating the existence of fitness costs. These costs were greatest for resistance against frugivores, moderate for florivores, and lowest for folivores. In addition, significant correlational selection gradients were found for ten pairs of resistance measures, which we interpret as evidence that the fitness impacts of these pairs of herbivores combined non-additively. When the herbivores fed on the same type of tissue, their impact was synergistic (greater than additive), and when they fed on different tissues, their impact was antagonistic (less than additive). We suggest this may be a general pattern for correlational selection on resistance to different herbivores.尽管多数植物防御理论的核心假设均认为植物抗性存在适合度代价（fitness costs），但野外条件下这类代价的检测始终颇具难度。一种有效但劳动密集型的检测手段，是量化野外种群中作用于抗性的稳定选择（stabilizing selection）。本研究以卡罗林茄（Solanum carolinense）为研究对象开展田间试验，针对9种植食者（herbivores），对12种抗性（操作定义为1减去组织受损比例）开展了二次表型选择分析（quadratic phenotypic-selection analysis）。结果显示，其中7种抗性存在显著的稳定选择与中间最优水平，这证实了适合度代价的存在。该代价的强度随抗性针对的植食类群而异：针对食果动物（frugivores）的抗性代价最高，针对食花动物（florivores）的次之，针对食叶动物（folivores）的最低。此外，我们在10对抗性指标中检测到了显著的相关选择梯度，据此可认为，这两类植食者的抗性对适合度的影响存在非加性组合效应：当植食者取食同一类型组织时，二者的影响呈协同效应（大于加性效应）；当它们取食不同类型组织时，其影响则呈拮抗效应（小于加性效应）。我们推测，这或许是针对不同植食者的抗性所受相关选择的普遍规律。