The dynamics of age-structured host-parasitoid interactions

SUMMARY (1) An age-structured simulation model is developed for interacting parasitoid and host populations characterized by the presence of overlapping stages and unequal generation times. The model is based on laboratory studies of two bruchid hosts, Callosobruchus chinensis and C. maculatus, and their pteromalid parasitoid Lariophagus distinguendus. (2) The host population model has been previously described, and to this is coupled a parasitoid model incorporating experimentally determined variations in adult searching efficiency with parasitoid age and host stage. (3) The predicted populations, using the estimated bruchid-parasitoid parameters, show erratic fluctuations in densities of both host and parasitoid, due to interactions amongst parasitism, competition and age-structure in the two populations. (4) The model results are compared to those from a long-term laboratory study by Utida (1950) using C. chinensis and another pteromalid parasitoid, Anisopteromalus calandrae. The experimental populations also showed erratic fluctuations that are qualitatively similar to those from the simulation model, suggesting that they too may arise from the internal dynamics of the interaction.

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