Transient host–parasitoid dynamics illuminate the practice of biological pest control
2012
Mills, Nicholas J.
[Formula: see text] [ The harlequin bug (Murgantia histrionica; top left) is a specialist herbivore on Isomeris arborea, an endemic plant species of the California coastal sage scrub ecosystem (top right). The bug's eggs (bottom center) are parasitized by two parasitoid natural enemies, Trissolcus murgantiae (bottom left) and Ooencyrtus johnsonii (bottom right). The harlequin bug and its parasitoids exhibit many attributes of pest‐enemy systems in general, and of Homopteran pest systems in particular. First, the bug is a specialist herbivore on a long‐lived host plant, similar to many Homopteran pests that attack long‐lived crop plants (e.g., citrus, olive, stone fruits), and its only natural enemies are the two specialist parasitoids. Second, the bug and parasitoids exhibit the same life history and population dynamics as Homopteran pest systems, with an invulnerable adult stage of the herbivore and a persistent host‐parasitoid interaction with host densities maintained at low levels. Third, the parasitoids engage in the same types of interactions as the natural enemies of Homopteran pests (exploitative competition and multiparasitism). Fourth, the bug is a minor pest of crucifers in the southeastern U.S. and the parasitoids are potential control agents. These attributes make this community an ideal model system for investigating the efficacy of natural enemies in pest suppression. ] Kidd, D. & Amarasekare, P. (2012) The role of transient dynamics in biological pest control: insights from a host–parasitoid community. Journal of Animal Ecology, 81, 47–57. Our current understanding of host–parasitoid relationships has been strongly influenced by the quest for stability and persistence, and consequently, is based on a large body of theory that has focused on the assumption of equilibrium dynamics. In an elegant analysis of a host–parasitoid model parameterized from laboratory observations, Kidd & Amarasekare broaden our understanding by contrasting the parameters that influence transient versus equilibrium dynamics. Their study highlights the importance of parasitoid handling time, competitive exclusion and intraspecific interference in the transient dynamics of a model host–parasitoid community.
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