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为抗性存在适合度代价（fitness cost），但学界始终难以在野外环境中检测到这类代价。一种虽耗时费力但颇具应用价值的检测方法，是对野外种群中作用于抗性的稳定选择（stabilizing selection）进行量化分析。本研究以卡罗林那茄（Solanum carolinense）为对象开展田间试验，针对9种植食性昆虫（herbivore）对应的12类抗性（操作定义为1减去组织受损比例）开展二次表型选择分析。针对其中7类抗性，我们检测到显著的稳定选择及中间最优水平，这一结果证实了适合度代价的存在。这类代价在针对食果类植食者（frugivore）的抗性中最为显著，针对食花类植食者（florivore）的抗性中次之，针对食叶类植食者（folivore）的抗性中最弱。此外，我们在10组抗性指标中检测到显著的相关选择梯度（correlational selection gradient），我们将其解读为：该组植食者对宿主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的组织时，其影响呈现协同效应（大于加性效应）；当它们取食不同类型的组织时，其影响则呈现拮抗效应（小于加性效应）。我们认为这或许是针对不同植食者抗性的相关选择所共有的普遍模式。