Pleiotropic opposing dominance within a color gene block contributes to a nascent species boundary via its influence on hybrid male territorial behavior.

The divergence of plumage color genes contributes to songbird radiation. However, the mechanisms by which color gene divergence counteracts gene flow to maintain reproductive isolation during the formation of new species boundaries remain elusive. The hybrid zone between (SOCC) and (STOW) in the Cascade Range provides a natural observatory to investigate potential behavioral mechanisms underlying divergent selection on color genes.

Selection on a small genomic region underpins differentiation in multiple color traits between two warbler species.

Speciation is one of the most important processes in biology, yet the study of the genomic changes underlying this process is in its infancy. North American warbler species and hybridize in a stable hybrid zone, following a period of geographic separation. Genomic differentiation accumulated during geographic isolation can be homogenized by introgression at secondary contact, whereas genetic regions that cause low hybrid fitness can be shielded from such introgression.