Parasitoid meta-community dynamics

Theory and empirical data indicate that forest structure (i.e., composition and configuration) can affect insect population dynamics and thus has the potential to modulate the severity and extent of forest insect outbreaks. Forest structure affects population irruptions directly through the availability and connectivity of suitable host trees. However, the forest can also indirectly affect outbreaks through its effects on predator (parasitoid) community diversity, abundances, and mobility. This project combines tools and techniques from community ecology and landscape genetics to evaluate the relative contributions of direct and indirect factors on insect trophic dynamics and outbreaks. Specifically, we are evaluating the relative importance of the “silvicultural” and “natural enemies” hypothesis of spruce budworm (SBW) outbreaks.

To address this idea, SBW larvae were collected in the summer of 2014 from 30 sites across Quebec in regions currently affected by the SBW. Larvae were reared and emerged parasitoids were identified. In total, or 50 000 larvae were individually reared which provided over 7000 parasitoids of over 15 species of hymenoptera and diptera.

Current projects using these data include:

1) Assessing how forest structure affects spatial variation in parasitism rates at different spatial scales using remotely sensed data.

2) Determining the relative importance of spatial context, environmental variation, and outbreak characteristics of parasitoid community beta-diversity at broad spatial scales.

3) Investigating how climate driven phenological mismatches between SBW and parasitoids may affect future outbreak dynamics in northern forests.

4) Characterizing the spatial genetic structure and estimating dispersal capacity of two parasitoid species: Apanteles fumiferanae & Glypta fumiferanae.

5) Assessing the context-dependent drivers of community assembly in the SBW parasitoid complex.

We hope that our results will contribute to our understanding of the diversity-stability relationships in forest insects systems and to provide recommendations for spatial management strategies that will allow us to augment the control that parasitoid populations exert on outbreaking populations and thus to reduce forest losses.

Selected Publications

Legault S & James PMA. 2024. Spatial patterns of hyperparasitism along a latitudinal gradient of forest diversity: Insights from the spruce budworm-parasitoids community. Environmental Entomology. 53(1): 116-126

Legault S, Wittische J, Cusson M, Brodeur J, James PMA. 2021. Genetic evidence of large-scale population connectivity in spruce budworm parasitoids. Molecular Ecology. 30(22), 5658-5673

Marrec R, Pontbriand-Paré O, Legault S, and James PMA. 2018. Spatiotemporal variation in drivers of parasitoid metacommunity structure in continuous forest landscapes. Ecosphere 9(1):e02075. doi: 10.1002/ecs2.2075