Document: MAR-3-23-4

Effects of plant heterogeneity on herbivore population dynamics: Density-dependent, density-independent, and inverse density-dependent effects.

HUNTER, M.D.*

University of Georgia, Athens, GA, 30602, USA ¹

Abstract:
It is well established that the natural enemies of insect herbivores can impose density-dependent, density-independent, and inverse density-dependent mortality on their prey. These types of mortality have been incorporated into both conceptual and mathematical models of insect herbivore population dynamics providing a backbone for much of our current population theory. However, plant responses to injury by insect herbivores can also result in the same range of density-dependent responses by phytophagous insect populations. The incorporation of such plant-based responses into population theory has received only limited attention. Examples are provided to demonstrate that herbivore populations are capable of expressing complex responses to variation in plant quality. Several suggestions for incorporating plant-driven population responses into conceptual and mathematical models are provided. With specific reference to insect herbivores of oak, interactions between plant-driven and enemy-driven density-dependent responses are shown to reflect more accurately population behavior under field conditions. It is concluded that a realistic theory of insect herbivore population dynamics should include density-dependent, density-independent, and inverse density-dependent responses to variation in plant quality as well as such responses to predation.

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This abstract is being presented at: 1:50 PM in session:
Symposium # 23: Why Variation is Not Just Noise: The Influence of Variability on Plant-Herbivore and Plant-Pathogen Interactions.