Plant architecture and leaf damage in bear oak II: Insect usage patterns

Bear oak bushes (Quercus ilicifolia) have an inside-outside architecture where there is a set of leaves partially or completely concealed within the bush by an exterior set of leaves. We examine the impact of this architecture on microhabitat differences that are important to insect herbivores. Furthermore, we document the patterns of usage by plant-feeding insects on the inside and outside of the bush in different areas of the pine barrens of Long Island, NY. We show that there is more leaf-chewing damage and more galls of the Cynipid wasp, Amphibilops ilicifolia, on the outside of the plant. This inside-outside pattern for leaf-chewing damage is consistent across different sites, though the degree of difference between the inside and outside varies by location. We suggest that the observed herbivory pattern may be generated by differential larval performance on the inside vs. the outside leaves, differential ovipositional choice between the inside vs. the outside of the bush, or both.