Document: WIL-3-23-2

Why strong induced resistance might NOT drive herbivore fluctuations: Intrinsic and extrinsic sources of spatial and temporal heterogeneity.

MORRIS, W.*

Duke University, Durham, NC 27708 USA ¹

Abstract:
Induced resistance, because it can lead to temporal variation in host plant quality, has the potential to cause herbivore population density to fluctuate over time. Yet it is difficult to identify unambiguous empirical examples of herbivore populations that fluctuate as a result of induced resistance. The driving force of induced resistance may be masked by other sources of heterogeneity that are both intrinsic to the plant-herbivore interaction and extrinsic to it. Intrinsic factors include both variation in host plant quantity (as distinct from quality) generated by herbivore feeding and fixed (genetic) differences in constitutive and inducible resistance among plants. Heterogeneity among plants that is generated by spatial and temporal variation in external environmental factors can also obscure the population-level effect of induced resistance, particularly when the herbivore's mobility is low to moderate. I illustrate these factors both by exploring population models explicitly designed for plant-herbivore interactions and by borrowing well-known results from models of host-parasitoid interactions. The ultimate goal is to pinpoint a more precise range of conditions in which we might hope to find real-world cases of herbivore fluctuations driven by induced resistance. In doing so, it will be critical to account for multiple sources of heterogeneity.

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This abstract is being presented at: 2:15 PM in session:
Symposium # 23: Why Variation is Not Just Noise: The Influence of Variability on Plant-Herbivore and Plant-Pathogen Interactions.