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Adaptive Superparasitism and Patch Time Allocation in Solitary Parasitoids: An ESS Model
Marcel E. Visser, Jacques J. M. Van Alphen and Lia Hemerik
Journal of Animal Ecology
Vol. 61, No. 1 (Feb., 1992), pp. 93-101
Published by: British Ecological Society
Stable URL: http://www.jstor.org/stable/5512
Page Count: 9
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1. The adaptive value of superparasitism (oviposition in a previously parasitized host) when solitary parasitoids deplete a patch simultaneously is investigated, using a deterministic game theoretical model in which encounter rates with host types, which differ in the number of parasitoid eggs they contain, change over time due to depletion. 2. Parasitoids should never superparasitize when they search a patch alone. 3. When parasitoids search in the presence of conspecifics, the evolutionarily stable strategy (ESS) is to reject parasitized hosts at first but later, after a threshold has been reached, to accept them. Different thresholds exist for hosts containing different numbers of eggs. 4. The thresholds are expressed in gross rate of offspring gain. 5. With an increasing number of parasitoids per patch, females should begin to superparasitize at higher rates of gain. 6. The gross rate of gain at which a parasitoid leaves the patch (the leaving threshold) influences the threshold rate at which they should begin to superparasitize. Patch time allocation and host acceptance decisions are interdependent. 7. Both the handling time and the pay-off from an egg laid in a parasitized host strongly influence the threshold rate at which parasitoids should begin to superparasitize. This threshold is only weakly influenced by the number of hosts in the patch. 8. The model predicts that patch time per female and degree of superparasitism are influenced by the number of females in a patch. 9. The total number of offspring gained per unit time in the patch decreases with the number of females, even when the patch area per female and the number of hosts per female are kept constant; thus, superparasitism leads to interference. 10. Experimental evidence is in qualitative agreement with the predictions of the model.
Journal of Animal Ecology © 1992 British Ecological Society