Figure 3: BFD* species delimitation and TreeMix introgression results using SNPs. The left panel in (A) depicts the BFD* “4 species” model visualized as both a maximum clade credibility (MCC) tree (overlaid in black), and as a “tree cloud” output by DensiTree (in colour), supporting northern and southern S. hesperis as distinct species. Posterior probability values are indicated in red at both nodes on the MCC tree, and grey values along the branches indicate the estimates of theta (=Ne ) for each lineage. The right panel in (A) visualizes the genealogical discordance between SNPs as the source of poor branch support for the S. zerene /southernS. hesperis clade on the MCC tree, and indicates three alternate relationships between S. zerene and S. atlantis/S. hesperis. Percentages above each DensiTree represent the proportion of trees in the posterior distribution depicting that topology. (B) depicts the maximum likelihood phylogeny (left) output by TreeMix using the populations recovered in the K = 6 Structure analysis (Fig. 2), with three statistically significant migration events showing putative introgression between populations of S. zerene, S. hesperis, andS. atlantis . The model residuals for this analysis are indicated by the heatmap on the right in (B).