Melanin-based coloration is a nondirectionally selected sex-specific signal of offspring development in the Alpine swift

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State: Public
Version: author
Serval ID
serval:BIB_95B3D92D6F41
Type
Article: article from journal or magazin.
Collection
Publications
Title
Melanin-based coloration is a nondirectionally selected sex-specific signal of offspring development in the Alpine swift
Journal
Evolution
Author(s)
Bize P., Gasparini J., Klopfenstein A., Altwegg R., Roulin A.
ISSN
0014-3820
Publication state
Published
Issued date
2006
Peer-reviewed
Oui
Volume
60
Number
11
Pages
2370-2380
Language
english
Abstract
Two mutually exclusive hypotheses have been put forward to explain the evolution and adaptive function of melanin-based color traits. According to sexual selection theory melanism is a directionally selected signal of individual quality, whereas theory on the maintenance of genetic polymorphism proposes that alternative melanin-based variants achieve equal fitness. Alpine swift (Apus melba) males and females have a conspicuous patch of white feathers on the breast with their rachis varying continuously from white to black, and hence the breast varies from white to striated. If this trait is a sexually selected signal of quality, its expression should be condition dependent and the degree of melanism directionally selected. If variation in melanism is a polymorphism, its expression should be genetically determined and fitness of melanin-based variants equal. We experimentally tested these predictions by exchanging eggs or hatchlings between randomly chosen nests and by estimating survival and reproduction in relation to melanism. We found that breast melanism is heritable and that the environment and body condition do not significantly influence its expression. Between 5 and 50 days of age nestlings were heavier and their wings longer when breast feathers of their biological father were blacker, and they also fledged at a younger age. This shows that aspects of offspring quality covary positively with the degree of melanism. However, this did not result in directional selection because nestling survival and recruitment in the local breeding population were not associated with father breast melanism. Furthermore, adult survival, age at first reproduction and probability of skipping reproduction did not covary with the degree of melanism. Genetic variation in breast melanism is therefore maintained either because nonmelanic males achieve fitness similar to melanic males via a different route than producing fast-growing offspring, or because the advantage of producing fast-growing offspring is not sufficiently pronounced to result in directional selection.
Keywords
Alpine swift, directional selection, growth rate, melanin-based coloration, sexual selection, signaling
Pubmed
Web of science
Create date
24/01/2008 17:42
Last modification date
20/08/2019 14:58
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