Host-plant Age, Phenology, and Vigor as Determinants of Herbivore Performance

以植物为食的昆虫通常在寄主植物之间或在单个寄主内分布不均匀。相反，某些宿主和宿主内的位置优先受到昆虫的攻击。在生长季节内取食的时间也经常受到限制。确定这些取食偏好与昆虫存活和繁殖力相关的程度，对于理解是什么因素引发和终止昆虫周期性暴发至关重要。这项拟议的研究将在明尼苏达州北部检测采叶蛾与其颤抖的杨树宿主树之间的相互作用，那里的蛾经常达到暴发密度。实验将测试矿工是否像目前的一些理论所说的那样，优先在树叶内的特定位置取食，或者以特别大和/或快速生长的树枝上的树叶为食；生长季节的取食分布是否与食草动物的表现相关；以及杨树在成熟后是否对食草动物产生抵抗力。食草性昆虫的暴发既发生在自然生态系统中，也发生在人类主导的生态系统中。这项研究解决了树叶品质的自然时空变化如何影响食草动物的表现以及种群暴发的可能性等关键问题。它详细说明了食草动物密度高在多大程度上导致了劣质资源的使用，而劣质资源是植食性昆虫种群动态的重要组成部分。此外，研究结果还将对杨树这一极具商业价值的树种的林分管理具有重要的指导意义。

Plant-feeding insects are generally not uniformly distributed among host plants or within individual hosts. Instead, certain hosts, and sites within hosts, are preferentially attacked by insects. The timing of feeding within a growing season is also frequently circumscribed. Determining the extent to which theses feeding preferences are correlated with insect survival and fecundity is crucial to understanding what factors trigger and terminate periodic outbreaks of insects. The proposed research will examine interactions between a leaf-mining moth and its quaking aspen host trees in northern Minnesota, where the moth frequently reaches outbreak densities. Experiments will test whether miners preferentially feed at particular sites within leaves, or on leaves on particularly large and/or rapidly growing shoots and branches, as some current theory suggests; if the distribution of feeding over the growing season is correlated with herbivore performance; and whether aspen trees develop resistance to herbivory as they mature. %%% Outbreaks of herbivorous insects occur both in natural & human dominated ecological systems.This research addresses pivotal questions concerning how natural temporal and spatial variation in foliage quality influences herbivore performance & potential for population outbreaks. It details the extent to which high herbivore density results in the use of inferior resources, an important component of the population dynamics of plant-feeding insects. In addition, the results will have important implications for management of stands of quaking aspen, a commercially valuable tree species.