| 1. |
- Dunn, Peter O., et al.
(författare)
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Carotenoid and melanin-based ornaments signal similar aspects of male quality in two populations of the common yellowthroat
- 2010
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Ingår i: Functional Ecology. - : Wiley. - 1365-2435 .- 0269-8463. ; 24:1, s. 149-158
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Tidskriftsartikel (refereegranskat)abstract
- P>1. Female preferences for particular male ornaments may shift between populations as a consequence of ecological differences that change the reliability and detectability of the ornament, but few studies have examined how ornaments function in different populations. 2. We examined the signalling function of male plumage ornaments in a warbler, the common yellowthroat (Geothlypis trichas), breeding in New York (NY) and Wisconsin (WI), USA. Males have two prominent ornaments: a black facial mask pigmented with melanin and a yellow bib pigmented by carotenoids. Previous studies in WI indicate that the size of the mask, and not the bib, is primarily related to female choice and male reproductive success. In NY, however, the pattern is reversed and attributes of the bib (size and colour), and not the mask, are the target of sexual selection. 3. We found that brightness of the yellow bib was the best signal of humoral immunity (immunoglobulin G) in NY and mask size was the best signal in WI, after controlling for breeding experience and capture date. Thus, similar aspects of male quality appeared to be signalled by different ornaments in different populations. 4. There was no difference between populations in the level of plasma carotenoids or the prevalence of malarial parasites, which may affect the costs and benefits of choosing males with particular ornaments in each location. 5. Even though females in different populations prefer different ornaments produced by different types of pigments, these ornaments appear to be signalling similar aspects of male quality. Our results caution against inferring the function of particular ornaments based simply on their type of pigment.
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| 2. |
- Garvin, Julia C, et al.
(författare)
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Do male ornaments signal immunity in the common yellowthroat?
- 2008
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Ingår i: Behavioral Ecology. - : Oxford University Press (OUP). - 1045-2249 .- 1465-7279. ; 19:1, s. 54-60
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Tidskriftsartikel (refereegranskat)abstract
- Male ornaments may advertise genetic benefits to females choosing mates. These benefits may come in the form of genes for resistance to parasites and disease. Thus, females that prefer more ornamented males as mates may receive genes for enhanced immune system function for their offspring. The common yellowthroat (Geothlypis trichas) is the only species to date in which a male plumage ornament (size of the black facial mask) is known to be related to extrapair mating, and extrapair young are more immunocompetent than their within-pair half-sibs (at least in colder years). To investigate whether male mask size signals superior immune function, we examined male ornaments (mask and bib size and color) in relation to measures of overall health (hematocrit) and immune system function (plasma immunoglobulin G [IgG] concentration and cutaneous immune activity). We also investigated the role that testosterone may play in mediating the relationship between ornaments and immunity. Male mask size was correlated positively with IgG level, suggesting that male mask size may indicate humoral immunity. However, mask size was correlated negatively with hematocrit and cutaneous immune activity (our measure of nestling immunocompetence). Bib size and color were not related to these indices of immune function or health. Plasma testosterone level was neither related to immune function or health nor to the expression of male ornaments. These results suggest that there might be a trade-off between immune system components, as well as between immunity and the production or advertisement of male ornaments.
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