TEMPORAL SPATIAL STRUCTURE AND THE DYNAMICAL PROPERTY OF LABORATORY HOST-PARASITOID SYSTEMS/

The effects of spatial structure in terms of local capacity, or the ma ximum number of larvae surviving competition at resource patches, and temporal structure in terms of the period vulnerable to parasitoid att ack in host populations on the persistence of host-parasitoid systems were quantitatively evaluated by laboratory experiments and well-param eterized model analyses. One of two bruchid beetles, Callosobruchus ma culatus and C. phaseoli, were used as a host with Heterospilus prosopi dis used as the parasitoid. C. maculatus, in which few larvae survive competition to become adults in each bean, and C. phaseoli, in which m any larvae become adults in each bean, along with two kinds of beans, the mung and the azuki, were combined to construct four (2x2) resource -herbivorous host-parasitoid systems that differed in local capacity a nd vulnerable period. The mung-C. maculatus system with the parasitoid was the most persistent, i.e., took the longest time for extinction o f either the host or parasitoid to occur. Since this resource-herbivor ous host combination exhibited the lowest local capacity and the short est vulnerable period, these two conditions possibly promoted the pers istence of the system. A model incorporating the host population struc ture supported the observed persistence. Furthermore, the possible con tribution of the timing of density-dependent competition of the host o n the host-parasitoid persistence is predicted.