Patch size and quality affect herbivore and predator colonization.
Piechnik, Denise*,1, 1 University of California, Davis, Davis, CA, USA
ABSTRACT- The resource concentration hypothesis suggests that specialist herbivores aggregate in increased densities, especially in patches with greater host plant concentrations. It follows that predators of these specialist herbivores will likely respond positively to these dense host aggregations. Other factors affecting herbivore and predator densities include patch quality and size. I examined how habitat size (2 plot sizes) and quality (1 level of fertilizer enrichment) influenced colonization order of aphids and their specialist predators (parasitoids). Both aphids and their predators had a mixed response to habitat size and quality. Smaller plots had slightly more aphids and more predators per unit area than larger plots. However, fertilizer-enriched plots had fewer aphids but a greater proportion was stung by parasitoids. My results suggest that the proportionately greater edge areas of smaller plots may expose prey and attract more parasitoids. Futhermore, increased habitat size and better quality may attract more predators (generalist and specialist), which may have suppressed aphids response to these habitat factors. Both trophic levels appear to be responding to increased resource concentration, but other factors such as edge effects and generalist predators should also be explored to explain these results.
Key words: Resource Concentration Hypothesis, Habitat Size and Quality, Aphids, Parasitoids
All materials copyright The Ecological Society of America (ESA), and may not be used without written permission.