Document: BRI-3-56-3

Polyphagous hosts and the stability of host-parasitoid interactions.

INOUYE, B.*

UC Davis, Davis CA USA 95616 95616 ¹

Abstract:
Many insect hosts attacked by parasitoids are generalist herbivores and eat a range of plant species. Studies have shown that the characteristics of a plant where an herbivore is feeding, such as trichomes, volatile compounds, and defensive compounds, can influence the likelihood of parasitoid searching and the final parasitoid attack rate. I present a simple model of a host and parasitoid population, based on the Nicholson-Bailey model, where the host feeds on, and the parasitoid searches on, two different plant types. In this model the herbivore population growth rates and parasitoid attack rates depend on the plant type where an herbivore feeds. I investigated the effects of variation in these parameters, and in the proportion of each plant type used and the fidelity of hosts and parasitoids to plant type across generations. Unlike the original Nicholson-Bailey model, which is always unstable, the interaction of a polyphagous host and a parasitoid can lead to stable or cyclic population dynamics. Stability is more likely when the parasitoid attack rates on the two plant types are more different, when hosts less often use the plant with the lower attack rate, and when host and parasitoid have low fidelity to plant type. Results of a literature review show that the parameter values necessary to obtain stability or cycles in the model are consistent with the range of host-plant effects observed in the field.

Keywords: host-parasitoid models, tritrophic, host-plant effects

This abstract is being presented at: 1:00 PM in session:
Oral Session #15: Parasitoids and Diseases.