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

Pierre Bize*, Julien Gasparini, Aurelie Klopfenstein, Res Altwegg, Alexandre Roulin

*Corresponding author for this work

Research output: Contribution to journalArticle

39 Citations (Scopus)

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.

Original languageEnglish
Pages (from-to)2370-2380
Number of pages11
JournalEvolution
Volume60
Issue number11
Publication statusPublished - Nov 2006

Keywords

  • Alpine swift
  • directional selection
  • growth rate
  • melanin-based coloration
  • sexual selection
  • signaling
  • MALE HOUSE SPARROWS
  • OWLS TYTO-ALBA
  • BARN OWL
  • PASSER-DOMESTICUS
  • PLUMAGE COLORATION
  • EASTERN BLUEBIRDS
  • MARKED ANIMALS
  • FEMALE
  • SURVIVAL
  • TRAITS

Cite this

Bize, P., Gasparini, J., Klopfenstein, A., Altwegg, R., & Roulin, A. (2006). Melanin-based coloration is a nondirectionally selected sex-specific signal of offspring development in the Alpine swift. Evolution, 60(11), 2370-2380.

Melanin-based coloration is a nondirectionally selected sex-specific signal of offspring development in the Alpine swift. / Bize, Pierre; Gasparini, Julien; Klopfenstein, Aurelie; Altwegg, Res; Roulin, Alexandre.

In: Evolution, Vol. 60, No. 11, 11.2006, p. 2370-2380.

Research output: Contribution to journalArticle

Bize, P, Gasparini, J, Klopfenstein, A, Altwegg, R & Roulin, A 2006, 'Melanin-based coloration is a nondirectionally selected sex-specific signal of offspring development in the Alpine swift', Evolution, vol. 60, no. 11, pp. 2370-2380.
Bize, Pierre ; Gasparini, Julien ; Klopfenstein, Aurelie ; Altwegg, Res ; Roulin, Alexandre. / Melanin-based coloration is a nondirectionally selected sex-specific signal of offspring development in the Alpine swift. In: Evolution. 2006 ; Vol. 60, No. 11. pp. 2370-2380.
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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.",
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T1 - Melanin-based coloration is a nondirectionally selected sex-specific signal of offspring development in the Alpine swift

AU - Bize, Pierre

AU - Gasparini, Julien

AU - Klopfenstein, Aurelie

AU - Altwegg, Res

AU - Roulin, Alexandre

PY - 2006/11

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N2 - 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.

AB - 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.

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KW - growth rate

KW - melanin-based coloration

KW - sexual selection

KW - signaling

KW - MALE HOUSE SPARROWS

KW - OWLS TYTO-ALBA

KW - BARN OWL

KW - PASSER-DOMESTICUS

KW - PLUMAGE COLORATION

KW - EASTERN BLUEBIRDS

KW - MARKED ANIMALS

KW - FEMALE

KW - SURVIVAL

KW - TRAITS

M3 - Article

VL - 60

SP - 2370

EP - 2380

JO - Evolution

JF - Evolution

SN - 0014-3820

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ER -