title: Testosterone activates sexual dimorphism including male-typical carotenoid but not melanin plumage pigmentation in a female bird.
abstract: In males it is frequently testosterone (T) that activates the expression of sexually selected morphological and behavioral displays, but the role of T in regulating similar traits in females is less clear. Here, we combine correlational data with results from T and gonadotropin-releasing hormone (GnRH) manipulations in both sexes to assess the role of T in mediating sexually dimorphic coloration and morphology in the red-backed fairy-wren (Malurus melanocephalus). We show that: (1) natural variation in female expression of ornamental traits (darkened bills and red back feathers) is positively associated with age and circulating androgen titres, (2) females have the capacity to express most male-typical traits in response to exogenous T, including carotenoid-pigmented body plumage, shorter feathers, darkened bill and enlarged cloacal protuberance, but (3) appear constrained in production of male-typical melanin-pigmented plumage, and (4) low androgen levels during the pre-nuptial molt, probably because of low ovarian capacity for steroid production (or luteinizing hormone sensitivity), prevent females from developing male-like ornamentation. Thus, females appear to retain molecular mechanisms for hormonally regulated male-typical ornamentation, although these are rarely activated because of insufficient production of the hormonal signal.
authors.affiliation: Department of Biological and Environmental Sciences, Göteborg University, Box 463, Göteborg 405 30, Sweden School of Biological Sciences and Center for Reproductive Biology, Washington State University, Pullman, Washington 99163, USA willowlindsay@gmail.com.
authors.forename: Willow R
authors.identifier: 0000-0001-8581-2558
authors.initials: WR
authors.lastname: Lindsay
authors.affiliation: School of Biological Sciences and Center for Reproductive Biology, Washington State University, Pullman, Washington 99163, USA Department of Biological Sciences, Arkansas Tech University, Russellville, AR 72801, USA.
authors.forename: Douglas G
authors.initials: DG
authors.lastname: Barron
authors.affiliation: Department of Neurobiology and Behavior and Cornell Laboratory for Ornithology, Cornell University, Ithaca, NY 14850, USA.
authors.forename: Michael S
authors.initials: MS
authors.lastname: Webster
authors.affiliation: School of Biological Sciences and Center for Reproductive Biology, Washington State University, Pullman, Washington 99163, USA.
authors.forename: Hubert
authors.initials: H
authors.lastname: Schwabl
mesh_terms: D000375:Aging / Q000502:physiology; D000728:Androgens / Q000097:blood; D000818:Animals; D002338:Carotenoids / Q000378:metabolism*; D005241:Feathers / Q000502:physiology*; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism; D008297:Male; D008543:Melanins / Q000378:metabolism*; D046109:Passeriformes / Q000033:anatomy & histology / Q000502:physiology*; D010641:Phenotype; D010858:Pigmentation / Q000187:drug effects*; D025341:Principal Component Analysis; D012727:Sex Characteristics; D013739:Testosterone / Q000494:pharmacology*
chemical_list: D000728:Androgens; D008543:Melanins; D007987:Gonadotropin-Releasing Hormone; D002338:Carotenoids; D013739:Testosterone
keywords: Bill color; Carotenoids; Melanins; Plumage color; Sexual dimorphism; Testosterone