The evolution of diapause in a coupled host-parasitoid system

Diapause of part of a population during a breeding opportunity is widespread among insects. We explore the evolution of such diapause in a coupled host-parasitoid system, using a discrete-generation population dynamic model that incorporates diapause. We show that diapause in the host tends to be a stabilizing factor while diapause in the parasitoid does not affect the stability boundaries. We then allow the frequency of diapause in the host and parasitoid to evolve, and find the joint population and evolutionary dynamic equilibrium by numerical methods. At the equilibrium, population dynamics exhibit cycles and host diapause always occurs. Parasitoid diapause often occurs, though this depends on exact parameter values. Thus, intrinsically generated fluctuations in fitness (due to cyclical population dynamics) lead to the evolution of diapause as a bet-hedging mechanism. (C) 1998 Academic Press.