Host-feeding and oviposition by parasitoids in relation to host stage: Consequences for parasitoid-host population dynamics |
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Authors: | N A C Kidd and M A Jervis |
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Institution: | (1) School of Pure & Applied Biology, University of Wales College of Cardiff, P. O. Box 915, CF1 3TL Cardiff, Wales, U. K. |
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Abstract: | Summary Among parasitoids which host-feed destructively, there is a tendency for females to partition their feeding and oviposition
behaviour in relation to different host stages, feeding preferentially or exclusively on earlier host stages and ovipositing
preferentially or exclusively in (or on) later ones. We explored the dynamic implications of this behaviour for parasitoid-host
population dynamics, using modifications of the age-structured simulation models of Kidd and Jervis (1989, 1991).
Using the new versions of the models, we compared the situation where parasitoids practice host stage discrimination with
respect to feeding and oviposition, with the situation where they do not. Additionally, we examined the effects of host stage
discrimination on populations by (a) having generations either discrete or overlapping, (b) varying initial age structure,
(c) having varying degrees of density dependence acting on host adult mortality, and (d) varying parasitoid develoment times
in relation to the length of host development.
With either discrete or overlapping generations of the host population, a reduction in the parasitoid development time had
a destabilizing influence on the parasitoid-host population interaction. With discrete generations stage discrimination had
no effect on the risk of extinction, irrespective of either the degree of density dependence acting on the host population,
or the initial age structure of the host population. When parasitoid search was uncoupled from the insect's adult energy requirements,
the interaction was always unstable. With continuous generations, stage discrimination affected stability at certain parasitoid
development times, but not at others. The relative lengths of parasitoid and host development times also influenced the tendency
of the host population to show discrete or overlapping generations. |
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Keywords: | parasitoids host-feeding oviposition population dynamics modelling |
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