Phylogeny of the three
strains used in this study based on seven conserved genetic regions. Rather than display each branch tip individually we have chosen to represent each of the three clusters with a composite triangle. The vertical height of the triangle indicates relative sample sizes for each strain examined in this study. The horizontal width of the triangle indicates the extent of intra-strain synonymous genetic diversity. The numbers along each branch indicate the observed number of synonymous substitutions per synonymous site (dS). The vertical order of the taxa displayed within each cluster is arbitrary.