Fig. 1.

Tracking S. sonnei after entering and establishing successive founder populations across Vietnam. North-orientated map of Vietnam shows the location of the study sites in Ho Chi Minh City (HCMC), Khanh Hoa (KH), and Hue; proposed pattern of geographical spread is indicated with arrows, and National Highway 1 is shown in white. Maximum-likelihood (ML) phylogeny for the Vietnamese S. sonnei is shown to the right, with divergence dates for major clones labeled (black internal nodes). Colors indicate location of isolation: red, HCMC; blue, Hue; and purple, KH. Where distinct locally evolving populations were detected, the local phylogenies are represented next to the city; blue and purple arrows indicate where these localized Hue and KH phylogenies fit within the larger tree.