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Monday, April 9 • 1:45pm - 2:00pm
INSECT & DISEASE OUTBREAKS: Temporal Variation in Spatial Genetic Structure During Population Outbreaks: Distinguishing Among Different Potential Drivers of Spatial Synchrony

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AUTHORS: Jeremy Larroque, Département de Sciences Biologiques, Université de Montréal; Simon Legault, Département de Sciences Biologiques, Université de Montréal; Rob Johns, Canadian Forest Service, Natural Resources Canada; Lisa Lumley, Royal Alberta Museum; Canadian Forest Service, Natural Resources Canada; Michel Cusson, Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre; Patrick M. A. James, Département de Sciences Biologiques, Université de Montréal

ABSTRACT: High periodic variations in population size are common across natural populations. In some cases, preventive management strategies could reduce economic losses associated with population outbreaks, requiring a clear understanding of the spatial population dynamics of irruptive species. However, factors governing their spatial dynamics are still not fully understood. It is generally considered that dispersal (“epicenter hypothesis”) and spatial correlation in environmental stochasticity (“oscillatory hypothesis” or Moran effect) can synchronize populations over wide areas. Our objective was to identify the relative support of these two mechanisms in the outbreaks of an economically important irruptive forest insect, the spruce budworm (Choristoneura fumiferana) in the province of Quebec (Canada). AMOVA, cluster analysis, isolation by distance and sPCA were used to characterize spatial and temporal genomic variation using 1370 SBW larvae sampled over four years (2012-2015) and genotyped at more than 190,000 SNP loci. We found evidence of weak spatial genetic structure at the scale of Quebec. The little structure that did exist decreased between 2012 and 2015. We also found genetic evidence of a long-distance dispersal event over > 140 km. Results thus suggest that dispersal is the key mechanism involved in driving population synchrony at this stage of the outbreak. Early intervention management strategies that aim to control source populations have the potential to be effective through limiting dispersal. However, the timing of such interventions relative to the outbreak cycles and local dynamics will greatly influence their probability of success.

Monday April 9, 2018 1:45pm - 2:00pm CDT
LaSalle 2 (7th Floor)