A genetic switch for male UV iridescence in an incipient species pair of sulphur butterflies

• DOI: 10.1073/pnas.2109255118
• Publication Date: 2022-01-10T21:25:47Z
• Authors: Vincent Ficarrotta; Joseph J. Hanly; Ling S. Loh; Caroline M. Franc...; Anna Ren; Kalle Tunström; Christopher W. Wheat; Adam H. Porter; Brian A. Counterman; Arnaud Martin
• Keywords: Iridescence; Reproductive isolation

Significance Incipient species are at an intermediate stage of speciation where reproductive isolation is counteracted by the homogenizing effects gene flow. Human activity sometimes leads such to reunite, as seen in Orange Sulphur butterfly, which forms large hybridizing populations with Clouded alfalfa fields. Here we show that sex chromosomes maintain these distinct, while rest their genome admixed. Sex notably determine males display females a bright, iridescent UV signal on wings. Genetic mapping, antibody stainings, and CRISPR knockouts collectively indicate bric brac controls whether UV-iridescent nanostructures develop each species, illustrating how master switch modulates male courtship signal.