Figure 1. Species tree based on multi-locus data showing phylogenetic relationships and approximate dates of divergence for all Sistrurus taxa [22] and Crotalus atrox and Agkistrodon c. contortrix outgroups [57].

Branch lengths for the in group taxa and Agkistrodon are as in Kubatko et al. [22]. Branch lengths for C. atrox were estimated based on mtDNA ATP6–8 gene sequence divergences between C. atrox [30] and S. miliarius and S. catenatus [22].