What happens to color and song genes in wood warblers sharing territory with a close relative?
Genes for color and song experience a rapid arms race to become distinct from the competitor.
When wood warblers coexist in the same geographical area (sympatry) with a close relative, the local selective pressures create what can be described as a rapid "arms race" concerning traits crucial for mating recognition, specifically color and song. Because hybridization is costly, natural selection rapidly favors individuals whose visual signals (color) and auditory signals (song) differ noticeably from the common local competitor. This localized fine-tuning drives rapid phenotypic divergence in these traits precisely where the species overlap, sharpening species boundaries in that specific region, even if they might look more similar when living separately (allopatry).
