PARENT SESSION
Oral Session #60: Agroecology- Sustainable Agriculture.
Presiding: R. Bohanan
Wednesday, August 7. 8:00 AM to 11:30 AM. Mesquite Room, Radisson.
Characterizing indirect interactions facilitated by a shared predator.
Harmon, Jason*,1, Andow, David1, 1 University of Minnesota, St. Paul, MN
ABSTRACT- Indirect interactions between generalist predators and alternative foods often make it difficult to predict predation on target prey. While alternatives can provide predators with valuable nutrition, they may distract predator foraging. Understanding how these mechanisms interact may help predict a given prey community's indirect effects. We studied the polyphagous coccinellid Coleomegilla maculata DeGeer and its predation of European corn borer eggs with the most common alternative foods in Minnesota maize: corn leaf aphids and corn pollen. Field cages and open plot experiments determined the influence of aphids and pollen on egg predation. Suitability feeding studies and preference experiments were performed in to interpret those results, but did not provide a characteristic to explain field patterns. Pollen was a marginal food source, yet reduced egg predation by half. Simple preference experiments revealed egg predation can be drastically reduced when aphids are present, yet in field experiments, aphids had little effect on egg predation. Experimental observations and a spatial model predict that food distribution in relation to predator foraging and movement can account for these seemingly counterintuitive results. Pollen is very abundant, frequently contacted, and provides frequent distractions. When C. maculata contacts aphids, enhanced localized foraging and increased aggregation may counteract greater time spent eating them. Understanding how prey characteristics influence the components of a predator's response may provide useful insights for predicting net indirect effects and mechanisms for their management.
KEY WORDS: indirect effect, apparent predation, generalist predator, biological control