Covariation between eumelanic pigmentation and body mass only under specific conditions |
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Authors: | Alexandre Roulin |
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Institution: | (1) Department of Ecology and Evolution, Biophore, University of Lausanne, 1024 Lausanne, Switzerland |
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Abstract: | Identifying the factors that mediate covariation between an ornament and other phenotypic attributes is important to determine
the signaling function of ornaments. Sign and magnitude of a covariation may vary across environments if the expression of
the ornament or of its linked genes regulating correlated phenotypes is condition-dependent. I investigated in the barn owl
Tyto alba whether sign and magnitude of covariation between body mass and two heritable melanin-based plumage ornaments change with
food supply, along the reproductive cycle and from the morning to the evening. Using a dataset of 1,848 measurements of body
mass in 336 breeding females, I found that females displaying large black spots were heavier than conspecifics with smaller
spots in the afternoon (i.e., a long time after the last feeding) but not in the morning (i.e., a short time after the last
feeding). This is consistent with the recently proposed hypothesis that eumelanin-based ornaments are associated with the
ability to maintain energy balance between food intake and energy expenditure. Thus, covariation between melanin-based coloration
and body mass can be detected only under specific conditions potentially explaining why it has been reported in only ten out
of 28 vertebrate species. The proposition that ornamented individuals achieve a higher fitness than drab conspecifics only
in specific environments should be tested for other ornaments. |
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Keywords: | Body mass Melanin-based coloration Polymorphism Sexual selection Female ornament |
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