Master of Science
Date of Defense
Robert J. Marquis, Ph.D.
I investigated how the survivorship, abundance, and development of two common microlepidoteran leaf-tiers on four species of oak change in response to leaf quality and exposure to the third trophic level, and used those results to validate predictions under the slow-growth-high-mortality hypothesis. In chapter 1, I begin with a review of the literature by examining the components of plant traits that contribute to the success of insect herbivores and how plants can alter both defensive compounds and nutritional quality in order to deter herbivory. I then describe how changes in leaf quality and defense can be overcome by insect herbivores, one means by which is shelter building. Finally, I introduce the slow-growth-high-mortality hypothesis and describe how plant quality, ecosystem engineering, and the third trophic level can be used to validate the predictions of said hypothesis. In chapter 2, I present the results of an experiment that examined the bottom-up and top-down effects on two common leaf-tying microlepidopterans on four species of oaks by manipulating their exposure to the third trophic level. I found that the two leaf-tier species experienced the first trophic level differently but responded similarly to the third trophic level. Plant traits differed among oak species and changed from one generation of leaf-tier to the next. However, plant traits, measured as principal components, were for the most part uncorrelated with measures of survivorship, development, and parasitism, and were, at the very most, inconsistent between the two leaf-tier species. The patterns of mortality for both leaf-tiers did not reflect the effects of tree identity on larval development and, hence, did not follow the predictions of the slow-growth-high-mortality hypothesis.
Barnett, Kirk Lee, "The ‘slow-growth-high-mortality’ hypothesis: how plant species, leaf quality, and the third trophic level contribute to the mortality of two common leaf-tying microlepidopteran herbivores" (2012). Theses. 47.