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Carotenoid‐Based Plumage Colors and Immune Function: Is There a Trade‐Off for Rare Carotenoids?


Fitze, Patrick; Tschirren, Barbara; Gasparini, Julien; Richner, Heinz (2007). Carotenoid‐Based Plumage Colors and Immune Function: Is There a Trade‐Off for Rare Carotenoids? The American Naturalist, 169(S1):S137-S144.

Abstract

Theory suggests that carotenoid‐based signals are used in animal communication because they contain specific information about parasite resistance or immunocompetence. This implies that honesty of carotenoid‐based signals is maintained by a trade‐off between pigmentation and immune function for carotenoids, assuming that the carotenoids used for coloration are also immunoenhancing. We tested this hypothesis by altering the diets of nestling great tits (Parus major) with supplementary beadlets containing the carotenoids that are naturally ingested with food or beadlets containing the carotenoids that are incorporated into the feathers; a control group received beadlets containing no carotenoids. We simultaneously immune challenged half of the nestlings of each supplementation group, using a two‐factorial design. Activation of the immune system led to reduced color expression. However, only nestlings fed with the naturally ingested carotenoids and not with the carotenoids deposited in the feathers showed an increased cellular immune response. This shows that the carotenoids used for ornamentation do not promote the immune function, which conflicts with the trade‐off hypothesis. Our results indicate that honesty of carotenoid‐based signals is maintained by an individual’s physiological limitation to absorb and/or transport carotenoids and by access to carotenoids, indicating that preferences for carotenoid‐based traits in sexual selection or parent‐offspring interactions select for competitive individuals, rather than specifically for immune function.

Abstract

Theory suggests that carotenoid‐based signals are used in animal communication because they contain specific information about parasite resistance or immunocompetence. This implies that honesty of carotenoid‐based signals is maintained by a trade‐off between pigmentation and immune function for carotenoids, assuming that the carotenoids used for coloration are also immunoenhancing. We tested this hypothesis by altering the diets of nestling great tits (Parus major) with supplementary beadlets containing the carotenoids that are naturally ingested with food or beadlets containing the carotenoids that are incorporated into the feathers; a control group received beadlets containing no carotenoids. We simultaneously immune challenged half of the nestlings of each supplementation group, using a two‐factorial design. Activation of the immune system led to reduced color expression. However, only nestlings fed with the naturally ingested carotenoids and not with the carotenoids deposited in the feathers showed an increased cellular immune response. This shows that the carotenoids used for ornamentation do not promote the immune function, which conflicts with the trade‐off hypothesis. Our results indicate that honesty of carotenoid‐based signals is maintained by an individual’s physiological limitation to absorb and/or transport carotenoids and by access to carotenoids, indicating that preferences for carotenoid‐based traits in sexual selection or parent‐offspring interactions select for competitive individuals, rather than specifically for immune function.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute of Evolutionary Biology and Environmental Studies
Dewey Decimal Classification:570 Life sciences; biology
590 Animals (Zoology)
Language:English
Date:2007
Deposited On:28 Mar 2013 16:02
Last Modified:05 Apr 2016 16:39
Publisher:University of Chicago Press
ISSN:0003-0147
Funders:Swiss National Science Foundation
Publisher DOI:https://doi.org/10.1086/510094

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