title: Plumage pigment differences underlying the yellow-red differentiation in the Northern Flicker (Colaptes auratus).
abstract: Elucidating the processes that create species differences is a central goal of evolutionary biology. The Northern Flicker (Colaptes auratus) exists as two well-differentiated subspecies groups in North America, the Yellow-shafted (auratus group) and Red-shafted Flickers (cafer group), which differ strikingly in the color of the underside and rachises of flight feathers, and of malar and nuchal patches. We investigated the physiological basis of these conspicuous phenotypic differences by identifying and quantifying the pigments involved. The yellow feathers of auratus contained carotenoids commonly found in nature (lutein, β-cryptoxanthin, zeaxanthin and β-carotene). The orange to red shafts/vanes of cafer and hybrids contained these carotenoids as well as mono- and diketo-carotenoids (notably adonirubin, α-doradexanthin, canthaxanthin, astaxanthin), representing oxygenated products at carbon C4(4') of the carotenoids present in auratus. Oxygenation of feather carotenoids at C4(4') correlated closely with shaft/vane redness. Carotenoid hydroxylation at C3(3') and the proportion of carotenoids with ε end-rings also varied with color and belie differences in the activity of several carotenoid-modifying enzymes between the two subspecies groups. Curiously, occasional yellow feathers in red-shafted individuals had the carotenoids of auratus, hence the differences are not constitutive in cafer, underscoring regulatory differences. The red malar stripe of cafer, the black malar stripe and red nuchal patch of auratus all contained similar types and amounts of carotenoids, mostly 3-hydroxy-4-keto-carotenoids. The biochemical differences between two strongly differentiated forms we uncovered shed light on how plumage coloration can change over evolutionary time and point to further avenues of research.
authors.affiliation: Royal Alberta Museum, 12845 -102 Avenue, Edmonton, AB T5N 0M6, Canada. Electronic address: jocelyn.hudon@gov.ab.ca.
authors.forename: Jocelyn
authors.initials: J
authors.lastname: Hudon
authors.affiliation: Department of Biology, University of Saskatchewan, Saskatoon, SK S7N 5E2, Canada.
authors.forename: Karen L
authors.initials: KL
authors.lastname: Wiebe
authors.affiliation: DISFARM, Sezione di Chimica Generale e Organica "A. Marchesini", Facoltà di Scienze del Farmaco, Università degli Studi di Milano, Via Venezian, 21, 20133 Milano, Italy.
authors.forename: Elena
authors.initials: E
authors.lastname: Pini
authors.affiliation: DISFARM, Sezione di Chimica Generale e Organica "A. Marchesini", Facoltà di Scienze del Farmaco, Università degli Studi di Milano, Via Venezian, 21, 20133 Milano, Italy.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Stradi
mesh_terms: D000818:Animals; D001717:Birds / Q000502:physiology*; D002338:Carotenoids / Q000032:analysis* / Q000737:chemistry; D005241:Feathers / Q000737:chemistry; D010858:Pigmentation
chemical_list: D002338:Carotenoids
keywords: 4-Oxygenase; Bird coloration; Carotenoids; HPLC; Hybrids