Testosterone and melanin-based black plumage coloration: a comparative study |
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Authors: | Veronika Bókony László Zsolt Garamszegi Katharina Hirschenhauser András Liker |
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Institution: | (1) Department of Ecology, Szent István University, Rottenbiller u. 50, 1078 Budapest, Hungary;(2) Department of Biology, University of Antwerp, U.A., Universiteitsplein 1, 2610 Wilrijk, Belgium;(3) Konrad Lorenz Research Station, 4645 Grünau, Austria;(4) Department of Limnology, University of Pannonia, Pf. 158, 8201 Veszprém, Hungary |
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Abstract: | Despite the functional significance of melanin-based plumage coloration in social and sexual signaling, the mechanisms controlling
its information content are poorly understood. The T-regulation hypothesis proposes that melanin ornaments signal competitive
abilities via the effects of testosterone (T) mediating both melanization and sexual/aggressive behaviors. Using the phylogenetic
comparative approach, we tested whether frontal black melanization is associated with elevated T around the time of breeding
plumage development across all bird species with available T-data. We found a context-dependent relationship between melanization
and T, varying with the type of ornamentation (patchy or full-black) and with the presumed taxonomic distribution of the hormonal
control of plumage dichromatism. Within two taxa in which male plumage development is assumed androgen-dependent (Charadriiformes,
Corvida), evolutionary increases in male melanization, and melanin dichromatism correlated with increases in T in most analyses
but not within the basal lineage (ratites, Galloanseriformes) with androgen-independent male plumage. Among Passeroidea with
presumably genetically or luteinizing-hormone-based male plumage, melanization and its dichromatism correlated with T only
in species with <100% frontal melanization. These results were robust as we controlled for several confounding variables such
as mating and parental behaviors. This study is the first to test and support the T-regulation hypothesis interspecifically,
suggesting that among-species differences in melanization may have evolved in response to differences in circulating T in
certain avian taxa. Our results imply that the extent of black ornamentation may serve as an honest indicator of male competitiveness
in those species that evolved an appropriate hormonal basis (T dependence) for color production.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. |
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Keywords: | Androgens Hormonal control Melanin ornaments Sexual selection Status signals |
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