Learning, host fidelity, and the stability of host-parasitoid communities

Simple models of host-parasitoid interactions show that a polyphagous parasitoid tends to drive extinct all but the most fecund of its hosts. Coexistence requires a mechanism by which hosts with lower fecundity can increase when rare. We explore how recently discovered parasitoid learning behavior can contribute to species coexistence. On emergence as adults, parasitoids learn chemical cues associated with their natal host and hence are more likely to locate and to oviposit in hosts of the same species. For two models incorporating different assumptions about parasitoid searching, we derive conditions for the strength of host fidelity that permits a feasible multihost equilibrium and argue that this equilibrium is stable whenever the corresponding single-host equilibria are stable.