Insect Herbivore Guild Interactions and Tall Thistle Population Dynamics: A Test of Conflicting Hypotheses

植物有各种各样的天敌，但对这些植物取食者(草食动物)之间相互作用的后果的定量预测仍然很困难。尚未解决的基本问题包括：(I)食草动物之间的相互作用如何影响植物种群？(2)相互作用是否具有协同或冲突的影响？以及，(Iii)结果取决于资源吗？迫切需要提高我们对这种相互作用的理解。这些信息对于我们对自然界中生物相互作用的基本理解是必不可少的。此外，了解这种相互作用对于推进有效的、环境安全的杂草生物防治具有实际意义。这个项目考察了本地昆虫与本地高蓟(高蓟)的相互作用，作为一个有四个特定目标的模型系统。这些是为了确定：(1)与主要类型的昆虫草食动物取食有关的植物表现是否不同；(2)草食动物对植物动态是否具有中性、协同或抑制作用；(3)结果是否与资源可获得性有关；以及(4)当前两种相互冲突的假说中，哪一种最能解释多种草食动物的影响。这些主要假设是：第一，当植物暴露在单一的、高效的昆虫食草动物物种中时，植物繁殖力和密度的减少最大；第二，当多种昆虫食草动物攻击不同的植物器官(例如根、叶、花)时，这些减少最大。这四个目标将通过沿着资源梯度密集测量自然高山锦鸡儿种群中的昆虫取食、通过昆虫排斥实验和开发积分投影模型来实现。这项研究具有重要意义，因为它解决了关于无处不在的生物相互作用的重要而未被探索的问题，因为它在杂草生物控制中具有实际应用。这一研究项目还将扩大农村社区学生的教育机会，农村社区学生是高等教育中代表性较低的群体。

Plants have a wide array of natural enemies, but the quantitative prediction of the consequences of interactions among these plant feeders (herbivores) remains difficult. Fundamental, unresolved questions include: (i) How do interactions among herbivores affect plant populations? (ii) Do interactions have synergistic or conflicting impacts? and, (iii) Does the outcome depend upon resources? There is an urgent need to improve our understanding of such interactions. The information is essential to our basic understanding of biological interactions in nature. Further, knowledge about such interactions has practical significance for advancing effective, environmentally safe biological control of weeds. This project examines the interaction of native insects with the native tall thistle (Cirsium altissimum) as a model system with four specific aims. These are to determine: (1) whether plant performance differs in relation to feeding by the main types of insect herbivores; (2) if herbivores have neutral, synergistic, or inhibitory effects on plant dynamics, (3) if the outcomes are related to resource availability; and (4) which of two current, conflicting hypotheses best explains the effects of multiple herbivores. These leading hypotheses are: first, that reductions in plant reproduction and density are highest when plants are exposed to a single, highly effective insect herbivore species; and, second, that these reductions are greatest when multiple insect herbivores attack different plant organs (e.g. roots, leaves, flowers). The four aims will be achieved by intensive measurement of insect feeding in natural C. altissimum populations along resource gradients, by insect exclusion experiments, and by development of an integral projection model. This research is significant because it addresses important, under-explored questions about ubiquitous biological interactions and because it has practical application in weed biocontrol. This research project also will expand educational opportunities for students from rural communities, an underrepresented group in higher education.