title: UV photoreceptors and UV-yellow wing pigments in Heliconius butterflies allow a color signal to serve both mimicry and intraspecific communication.
abstract: Mimetic wing coloration evolves in butterflies in the context of predator confusion. Unless butterfly eyes have adaptations for discriminating mimetic color variation, mimicry also carries a risk of confusion for the butterflies themselves. Heliconius butterfly eyes, which express recently duplicated ultraviolet (UV) opsins, have such an adaptation. To examine bird and butterfly color vision as sources of selection on butterfly coloration, we studied yellow wing pigmentation in the tribe Heliconiini. We confirmed, using reflectance and mass spectrometry, that only Heliconius use 3-hydroxy-DL-kynurenine (3-OHK), which looks yellow to humans but reflects both UV- and long-wavelength light, whereas butterflies in related genera have chemically unknown yellow pigments mostly lacking UV reflectance. Modeling of these color signals reveals that the two UV photoreceptors of Heliconius are better suited to separating 3-OHK from non-3-OHK spectra compared with the photoreceptors of related genera or birds. The co-occurrence of potentially enhanced UV vision and a UV-reflecting yellow wing pigment could allow unpalatable Heliconius private intraspecific communication in the presence of mimics. Our results are the best available evidence for the correlated evolution of a color signal and color vision. They also suggest that predator visual systems are error prone in the context of mimicry.
authors.affiliation: Department of Ecology and Evolutionary Biology, University of California, Irvine, California 92697, USA.
authors.forename: Seth M
authors.initials: SM
authors.lastname: Bybee
authors.forename: Furong
authors.initials: F
authors.lastname: Yuan
authors.forename: Monica D
authors.initials: MD
authors.lastname: Ramstetter
authors.forename: Jorge
authors.initials: J
authors.lastname: Llorente-Bousquets
authors.forename: Robert D
authors.initials: RD
authors.lastname: Reed
authors.forename: Daniel
authors.initials: D
authors.lastname: Osorio
authors.forename: Adriana D
authors.initials: AD
authors.lastname: Briscoe
mesh_terms: D000819:Animal Communication; D000818:Animals; D005075:Biological Evolution; D001717:Birds / Q000502:physiology; D002080:Butterflies / Q000145:classification* / Q000235:genetics / Q000502:physiology*; D055253:Color Vision; D019143:Evolution, Molecular; D005123:Eye / Q000378:metabolism; D020440:Gene Duplication; D007737:Kynurenine / Q000031:analogs & derivatives / Q000502:physiology*; D008800:Mexico; D008954:Models, Biological; D008969:Molecular Sequence Data; D055355:Opsins / Q000235:genetics / Q000502:physiology; D017956:Photoreceptor Cells, Invertebrate / Q000502:physiology; D020419:Photoreceptor Cells, Vertebrate / Q000502:physiology; D010802:Phylogeny; D010858:Pigmentation; D016133:Polymerase Chain Reaction; D011235:Predatory Behavior; D017422:Sequence Analysis, DNA; D013045:Species Specificity; D013053:Spectrophotometry; D014796:Visual Perception; D014921:Wings, Animal / Q000502:physiology
chemical_list: D055355:Opsins; D007737:Kynurenine