Variation in plant quality and the population dynamics of herbivores: there is nothing average about aphids |
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Authors: | Email author" target="_blank">Sandra?E?HelmsEmail author Mark?D?Hunter |
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Institution: | (1) Institute of Ecology, University of Georgia, Athens, GA 30602-2202, USA |
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Abstract: | In the attempt to use results from small-scale studies to make large-scale predictions, it is critical that we take into account
the greater spatial heterogeneity encountered at larger spatial scales. An important component of this heterogeneity is variation
in plant quality, which can have a profound influence on herbivore population dynamics. This influence is particularly relevant
when we consider that the strength of density dependence can vary among host plants and that the strength of density dependence
determines the difference between exponential and density- dependent growth. Here, we present some simple models and analyses
designed to examine the impact of variable plant quality on the dynamics of insect herbivore populations, and specifically
the consequences of variation in the strength of density dependence among host plants. We show that average values of herbivore
population growth parameters, calculated from plants that vary in quality, do not predict overall population growth. Furthermore,
we illustrate that the quality of a few individual plants within a larger plant population can dominate herbivore population
growth. Our results demonstrate that ignoring spatial heterogeneity that exists in herbivore population growth on plants that
differ in quality can lead to a misunderstanding of the mechanisms that underlie population dynamics. |
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Keywords: | Density dependence Plant– insect interactions Plant quality Population dynamics Spatial scale |
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