Fig. 4.
Derived optix CREs spread through introgression and mark loci of population differentiation at hybrid zones. (A) All annotated optix CREs show evidence of strong population differentiation in one or more hybrid zones. To reduce the effect of linked selection on evidence of population differentiation, the heatmap presents the mean SNP Fst of the entire optix locus (black bar) subtracted from the mean SNP Fst within a CRE. (B) Maximum likelihood phylogenies of distal optix CREs obs132, LR1, LR2, and obs214 form distinct clades for radiate populations (orange samples). (C) Collapsed phylogeny for Amazonian clade butterflies gives a summary of coalescent models for U2, obs132, LR1, and obs214, indicating that the radiate phenotype is derived from the basal postman morph and spread via introgression through the Amazonian populations.