Figure 2. Time-scaled phylogeny and discrete phylogeographic diffusion of HTLV-1 lineages in study of emergence of West African HTLV-1aC subgroup, Brazilian Amazon. A) Time-calibrated maximum clade credibility tree inferred in BEAST version 10.5 (https://beast.community) from the long terminal repeat (LTR) dataset (3 sequences from this study plus reference sequences), using sampling year as tip date, a strict molecular clock, and discrete geographic-state reconstruction under a continuous-time Markov chain model with Bayesian stochastic search variable selection. Branches and tips are colored by inferred location (see key); red tips indicate sequences generated in this study. B) Spatiotemporal diffusion reconstructed from Markov jumps. Trajectory colors correspond to each Manaus lineage: orange, SSS850_BrMao; green, WDM1168_BrMao; blue, WQC1199_BrMao. Numbers indicate posterior median year of first arrival (labels shown for years >1970; Cameroon→Japan step, ≈1928, is retained for context). Line style indicates support: dashed, no Bayers factor recovered; solid, weak support (<3; here, 0.2–0.4). Shaded polygons indicate inferred arrival locations (Amazonas and Pará states, Brazil, and Japan). HTLV, human T-lymphotropic virus.