Assigning phenologically asynchronous moths to source populations using individual genotypes

The spruce budworm (Choristoneura fumiferana; SBW) is a major forest pest in North America that causes extensive tree defoliation and mortality during periodic outbreaks. A key question in SBW ecology is how these outbreaks become synchronized over large areas. This study explores the role of long-distance dispersal in outbreak dynamics by analyzing genetic differences between local larvae and adult moths collected throughout a single flight season. Using Genotyping-by-Sequencing and a novel machine learning method, we identified subtle but significant genetic differences between resident and migrant moths and assigned migrants to likely source populations. Our results reveal complex dispersal patterns and overlapping genetic clusters, supporting the idea that long-distance movement contributes to regional outbreak synchrony.