DISSERTATION RESEARCH: Predicting the Combined Effects of Plant Resistance and Natural Enemies on Plant Fitness

植物通常会产生化学防御，减少食草动物的取食，但这些化学物质也可能对捕食者产生负面影响，捕食者通过攻击食草动物，也减少了食草动物对植物的损害。这项研究询问植物防御对捕食者的负面影响是否足以导致更多的化学防御植物生长不佳或产生更少的种子；此外，PI将检测化学防御与捕食者之间的干扰程度是否对不同类型的植物、草食动物和捕食者有所不同。利用甲虫以大豆植株为食，早期的研究发现，与防御严密的植物相比，捕食者在减少食草动物危害和增加种子产量方面比在防御严密的植物上更有效。在这项研究中，我们将探索大豆防御对捕食者的负面影响是否受到化学防御类型(永久性与暂时性)、食草动物的食物广度(单一植物与多种植物)以及捕食者的取食方式(外部捕食猎物与内部寄生虫)的影响。这些实验可能有助于解释为什么一些植物物种只有在受到食草动物伤害后才产生防御，而其他植物总是受到防御。这些实验的结果应该会提高我们对植物化学防御何时会增强或削弱捕食者攻击草食动物时植物获得的积极好处的理解，还可能有助于确定何时释放捕食者来控制大豆和其他农业植物上的害虫可能或多或少有效。

ABSTRACTPlants often produce chemical defenses that reduce herbivore feeding, but those chemicals may also have a negative effect on predators which, by attacking herbivores, also reduce herbivore damage to plants. This research asks whether the negative effect of plant defense on predators is sufficient to cause more chemically defended plants to grow less well or to produce fewer seeds; in addition, the PIs will detect whether the degree of interference between chemical defense and predators differs for different types of plants, herbivores, and predators. Using beetles feeding on soybean plants, earlier work found that a predator was more effective in decreasing herbivore damage and increasing seed production on plants with few resistance chemicals than on heavily defended plants. In this research, we will explore whether the negative effect of soybean defense on predators is influenced by the type of chemical defense (permanent vs. transient), the diet breadth of the herbivore (a single vs. multiple plant species), and the predator's feeding method (consuming the prey externally vs. as an internal parasite). These experiments may help to explain why some plant species produce defenses only after they receive herbivore damage, while other plants are always defended. The results of these experiments should improve our understanding of when plant chemical defense will enhance or detract from the positive benefits plants receive when predators attack herbivores, and could also could help to determine when releasing predators to control insect pests on soybeans and other agricultural plants may be more or less effective.