The tips of the trees correspond to the year of sampling while the branch (and node) colours reflect location: the sampling location for the tip branches and the inferred location for the internal branches (AF, Africa; CB, Caribbean; US, the United States; CA, California, GA, Georgia; NY, New York). The diameters of the internal node circles reflect posterior location probability values. Thick outer circles represent internal nodes with posterior probability support > 0.95. Grey bars indicate the 95% credibility intervals for the internal node ages. The tree in b) represents the fully annotated version of the tree in Fig. 1 in the main manuscript.