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, 7 (12), e53066

Immune Investment Is Explained by Sexual Selection and Pace-Of-Life, but Not Longevity in Parrots (Psittaciformes)


Immune Investment Is Explained by Sexual Selection and Pace-Of-Life, but Not Longevity in Parrots (Psittaciformes)

Darryl B Edwards. PLoS One.


Investment in current reproduction should come at the expense of traits promoting future reproduction, such as immunity and longevity. To date, comparative studies of pace-of-life traits have provided some support for this, with slower paced species having greater immune function. Another means of investment in current reproduction is through secondary sexual characters (SSC). Investment in SSC's is considered costly, both in terms of immunity and longevity, with greater costs being borne by species with more elaborate traits. Yet within species, females prefer more ornate males and those males are typically immunologically superior. Because of this, predictions about the relationship between immunity and SSC's across species are not clear. If traits are costly, brighter species should have reduced immune function, but the opposite is true if SSC's arise from selection for more immunocompetent individuals. My approach was to investigate immune investment in relation to SSC's, pace-of-life and longevity while considering potentially confounding ecological factors. To do so I assessed leukocyte counts from in a novel group, the Psittaciformes. Investment in SSC's best explained investment in immunity: species with brighter plumage had higher leukocyte counts and those with a greater degree of sexual dichromatism had fewer. Ecological variables and pace-of-life models tended to be poor predictors of immune investment. However, shorter incubation periods were associated with lower leukocyte counts supporting the notion that species with a fast pace-of-life invest less in immunity. These results suggest that investment in reproduction in terms of fast pace-of-life and sexual dichromatism results in reduced immunity; however, investment in plumage colour per se does not impose a cost on immunity across species.

Conflict of interest statement

Competing Interests: The author has declared that no competing interests exist.

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    1. Lochmiller RL, Deerenberg C (2000) Trade-offs in evolutionary immunology: Just what is the cost of immunity? Oikos 88: 87–98 (doi:10.1034/j.1600-0706.2000.880110.x) - DOI
    1. Norris K, Evans MR (2000) Ecological immunology: life history trade-offs and immune defense in birds. Behav Ecol 11: 19–26 (doi:10.1093/beheco/11.1.19) - DOI
    1. Williams GC (1966) Natural selection, the costs of reproduction, and a refinement of Lack's principle. Am Nat 100: 687–690 (doi:10.1086/282461) - DOI
    1. Stearns SC (1992) The evolution of life histories. Oxford,UK: Oxford University Press. 262p.
    1. Råberg L, Nilsson J, Ilmonen P, Stjernman M, Hasselquist D (2000) The cost of an immune response: vaccination reduces parental effort. Ecol Lett 3: 382–386 (doi:10.1046/j.1461-0248.2000.00154.x) - DOI

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Grant support

This work was supported by the Natural Sciences and Engineering Research Council of Canada: PGLS D Scholarship. The NSERC had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.