High-order mobile predators are generally thought to increase ecosystem stability and resilience to natural perturbations. In many insect food-webs, higher trophic positions are occupied by parasitoids, which are themselves hosts for hyperparasitoids that can reduce primary parasitoids' efficiency in controlling insect pests. Hyperparasitoids can thus provide ecosystem disservices by facilitating pest outbreaks, or ecosystem services by stabilizing food web fluctuations over longer time periods. To better understand how hyperparasitism affects multitrophic forest systems, we examined for the first time spatial variations in hyperparasitism associated with the spruce budworm. We examined 2 common primary parasitoids of the spruce budworm during outbreaks (Apanteles fumiferanae and Glypta fumiferanae), and estimated their true and pseudohyperparasitism rates in 2014-2015 from 28 locations across a latitudinal gradient (over 450 km) of forest genus diversity. Hyperparasitoid cryptic diversity was also quantified using DNA-barcoding. We found that A. fumiferanae and G. fumiferanae share at least 2 of 5 common hyperparasitoid species, confirming the connected nature of the spruce budworm-parasitoid food web. Moreover, hyperparasitism is modulated by spatial context as we observed a positive correlation between forest genus diversity and hyperparasitism for A. fumiferanae, but not for G. fumiferanae. Further monitoring hyperparasitism holds significant potential to provide new insights into how forest composition affects multitrophic interactions and spatio-temporal outbreak dynamics.
Keywords: DNA-barcoding; food-web; forest landscape; indirect interaction; insect outbreak.
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