VCF files of loci in approximate linkage equilibrium for two common spruce budworm larval parasitoids: Apanteles fumiferanae (Hymenoptera: Braconidae) and Glypta fumiferanae (Hymenoptera: Ichneumonidae)

Periodic and spatially synchronous outbreaks of insect pests have dramatic
consequences for boreal and sub-boreal forests. Within these multitrophic
systems, parasitoids 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 ability to predict forest
resilience in the context of global changes. In this study, we investigate
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
connectivity for both species, matching the previously described genetic
structure of the spruce budworm within the same context, suggesting
similar effective dispersal during 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 dynamics
should be considered when predicting future insect outbreak severities in
boreal landscapes.