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).