Canadian Forest Service Publications

Landscape-scale population connectivity in two parasitoid species associated with the spruce budworm: Testing the birdfeeder effect using genetic data. 2021. Legault S.; Wittische J.; Cusson M.; Brodeur J.; James P.; Molecular Ecology. 30: 5658–5673.

Year: 2021

Issued by: Laurentian Forestry Centre

Catalog ID: 40617

Language: English

Availability: PDF (request by e-mail)

Available from the Journal's Web site.
DOI: 10.1111/mec.16160

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Periodic and spatially synchronous outbreaks of insect pests have dramatic conse-quences for boreal and sub- boreal forests. Within these multitrophic systems, para-sitoids can be stabilizing agents by dispersing toward patches containing higher host density (the so-called birdfeeder effect). However, we know little about the dispersal abilities of parasitoids in continuous forested landscapes, limiting our understanding of the spatiotemporal dynamics of host–parasitoid systems, and constraining our abil-ity to predict forest resilience in the context of global changes. In this study, we in-vestigate the spatial genetic structure and spatial variation in genetic diversity of two important species of spruce budworm larval parasitoids during outbreaks: Apanteles fumiferanae Viereck (Braconidae) and Glypta fumiferanae (Viereck) (Ichneumonidae). Using parasitoids sampled in 2014 from 26 and 29 locations across a study area of 350,000 km2, we identified 1,012 and 992 neutral SNP loci for A. fumiferanae(N= 279 individuals) and G. fumiferanae (N= 382), respectively. Using DAPC, PCA, AMOVA, and IBD analyses, we found evidence for panmixia and high genetic con-nectivity for both species, matching the previously described genetic structure of the spruce budworm within the same context, suggesting similar effective dispersal dur-ing outbreaks and high parasitoid population densities between outbreaks. We also found a significant negative relationship between genetic diversity and latitude for A. fumiferanae but not for G. fumiferanae, suggesting that northern range limits may vary by species within the spruce budworm parasitoid community. These spatial dynam-ics should be considered when predicting future insect outbreak severities in boreal landscapes.