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- Title
Can hyperparasitoids cause large-scale outbreaks of insect herbivores?
- Authors
Nenzén, Hedvig K.; Martel, Véronique; Gravel, Dominique
- Abstract
Synchronous population fluctuations occur in many species and have large economic impacts, but remain poorly understood. Dispersal, climate and natural enemies have been hypothesized to cause synchronous population fluctuations across large areas. For example, insect herbivores cause extensive forest defoliation and have many natural enemies, such as parasitoids, that may cause landscape-scale changes in density. Between outbreaks, parasitoid-caused mortality of hosts/herbivores is high, but it drops substantially during outbreak episodes. Because of their essential role in regulating herbivore populations, we need to include parasitoids in spatial modelling approaches to more effectively manage insect defoliation. However, classic hostparasitoid population models predict parasitoid density, and parasitoid density is difficult to relate to host-level observations of parasitoid-caused mortality. We constructed a novel model to study how parasitoids affect insect outbreaks at the landscape scale. The model represents metacommunity dynamics, in which herbivore regulation, colonisation and extinction are driven by interactions with the forest, primary parasitoids and hyperparasitoids. The model suggests that parasitoid spatial dynamics can produce landscape-scale outbreaks. Our results propose the testable prediction that hyperparasitoid prevalence should increase just before the onset of an outbreak because of hyperparasitoid overexploitation. If verified empirically, hyperparasitoid distribution could provide a biotic indicator that an outbreak will occur.
- Subjects
INSECTS; HERBIVORES; DEFOLIATION; PARASITOIDS; ECONOMIC impact
- Publication
Oikos, 2018, Vol 127, Issue 9, p1344
- ISSN
0030-1299
- Publication type
Article
- DOI
10.1111/oik.05112