Darwinian and Wallacean evolution both explain sexual dichromatism in avian iridescence.

Across 3,151 bird species, iridescent sexual dichromatism in 25,432 color patches is explained by both Darwin and Wallace, with Darwin’s hypothesis more strongly supported.

• Why it matters: The Darwin–Wallace dispute over which sex changes color over time remains unresolved, and iridescence offers a repeated, conspicuous system tied to sexual selection and ecology.
• What they did: The study analyzed iridescent coloration data from 3,151 bird species, using 25,432 patches to test evolutionary origins of sexual dichromatism and to link patterns to sexual selection and nest safety.
• The result: Results indicate both hypotheses fit, but males contribute more strongly to evolutionary shifts in dichromatism, and the patterns align with sexual selection plus nest safety effects, especially in incubation-exposed patches.

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