Date of Award

Spring 1-1-2014

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Geological Sciences

First Advisor

Dena Smith

Second Advisor

Robert Guralnick

Third Advisor

Mary Kraus

Fourth Advisor

Herbert Meyer

Fifth Advisor

César Nufio

Abstract

Studies of insect herbivory in modern ecosystems have shown that climatic shifts can lead to changes in insect feeding behavior. This also has been found to be true for plant communities preserved in the fossil record, but hasn't been examined in a way that takes into account the coevolution of host-herbivore systems. Examining the pattern of feeding in insects that use a restricted group of host plants is important because insects that are highly specialized are thought to have different levels of climatic sensitivity than generalist herbivores. The relative influences of climate and coevolution can only be examined by following specific host taxa and the feeding damage made by their insect herbivores through time.

In this work, I focus on species of oak (Quercus) and follow their patterns of leaf herbivory across 25 floras from western North America, with ages ranging from the Eocene to the present. This set of floras captures the evolution of leaf herbivory made by insects across time and through different climatic regimes. I find numerous types of specialized insect damage that recur on the same oak hosts over time, indicating strong specialization and host-fidelity. These results suggest that while there are likely to be effects of climate on herbivory, that the relationship is not a simple one, and that by focusing our studies only at the community level, we miss nuances and risk creating models with limited predictive power.

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