Supplementary material for: A mosaic of modular variation at a single gene underpins convergent plumage coloration

The combination of genomic variation from multiple origins is an important contributor to phenotypic diversification, yet insights into the evolutionary trajectories of this combinatorial process and their interplay with genetic architecture remain scarce. We show that convergent color evolution in wheatears involves a monogenic architecture with modular variation introgressed at the agouti signalling protein (ASIP) locus. Introgression of a novel transposable element insertion and linked protein-coding variation underpin a trans-specific throat color polymorphism, which stable isotopes suggest are associated with alternative foraging niches. Co-introgression of linked regulatory ASIP variation resulted in mantle color convergence in one species, while convergent color evolution at the genus level required novel variation. Our results illustrate evolutionary trajectories from pre-existing variation realized within the constraints of a monogenic architecture.