Testosterone Activates Sexual Dimorphism Including Male-Typical Carotenoid but not Melanin Plumage Pigmentation in a Female Bird

Document Type

Article

Publication Date

10-1-2016

Department

Biological Sciences

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 gonadotropinreleasing 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.

DOI

10.1242/jeb.135384

First Page

3091

Last Page

3099

Publication Title

Journal of Experimental Biology

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