Fig. 2

Analysis of introduction events. A Introduction event origins as a percentage of the total inferred by each method. B Number of introduction events by region of origin inferred by self-reported travel history, phylogenetic ancestral state reconstruction, or both combined. For phylogeny-only and combined estimates, the points represent the ML estimate, while the bars indicate the difference between DELTRAN and ACCTRAN estimates (as lower and upper bounds). “Canada” refers to importations from other provinces into Québec. “Unclear” implies no travel history was available and ASR was ambiguous. C Travel-related sequences and the TMRCAs of inferred introductions into Québec over time by geographic origin. Dark densities: small points indicate sampling dates of sequenced cases with travel history. Large black points indicate the sampling date of the first sequenced case associated with each region. Pale densities: small points indicate the TMRCA of the inferred introductions using phylogeny and travel history (thus the date of introduction into Québec will be later). Triangles are the TMRCA of the first inferred introduction from each region into Québec, based on the phylogeny. Asterisks indicate uncertainty due to stem singletons in a large polytomy. The number of introductions is normalized to a relative density within each geographic category (rows). Grey bar is the spring break period in Québec