Genetic and environmental variation in condition, cutaneous immunity, and haematocrit in house wrens

Life-history studies of wild bird populations often focus on the relationship between an individual's condition and its capacity to mount an immune response, as measured by a commonly-employed assay of cutaneous immunity, the PHA skin test. In addition, haematocrit, the packed cell volume in re...

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Bibliographic Details
Published in:BMC evolutionary biology 2014-12, Vol.14 (1), p.242-242, Article 242
Main Authors: Sakaluk, Scott K, Wilson, Alastair J, Bowers, E Keith, Johnson, L Scott, Masters, Brian S, Johnson, Bonnie G P, Vogel, Laura A, Forsman, Anna M, Thompson, Charles F
Format: Article
Language:English
Subjects:
Analysis
Animal behavior
Animal populations
Animals
Animals, Wild
Biology
Bird migration
Bird populations
Ecology
Environmental aspects
Female
Genetic aspects
Genetic Variation
Hematocrit - veterinary
Immune response
Male
Morphology
Pedigree
Physiological aspects
Physiology
Selection, Genetic
Sex Determination Analysis
Skin - immunology
Songbirds - genetics
Songbirds - immunology
Songbirds - physiology
Studies
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Summary:Life-history studies of wild bird populations often focus on the relationship between an individual's condition and its capacity to mount an immune response, as measured by a commonly-employed assay of cutaneous immunity, the PHA skin test. In addition, haematocrit, the packed cell volume in relation to total blood volume, is often measured as an indicator of physiological performance. A multi-year study of a wild population of house wrens has recently revealed that those exhibiting the highest condition and strongest PHA responses as nestlings are most likely to be recruited to the breeding population and to breed through two years of age; in contrast, intermediate haematocrit values result in the highest recruitment to the population. Selection theory would predict, therefore, that most of the underlying genetic variation in these traits should be exhausted resulting in low heritability, although such traits may also exhibit low heritability because of increased residual variance. Here, we examine the genetic and environmental variation in condition, cutaneous immunity, and haematocrit using an animal model based on a pedigree of approximately 2,800 house wrens. Environmental effects played a paramount role in shaping the expression of the fitness-related traits measured in this wild population, but two of them, condition and haematocrit, retained significant heritable variation. Condition was also positively correlated with both the PHA response and haematocrit, but in the absence of any significant genetic correlations, it appears that this covariance arises through parallel effects of the environment acting on this suite of traits. The maintenance of genetic variation in different measures of condition appears to be a pervasive feature of wild bird populations, in contradiction of conventional selection theory. A major challenge in future studies will be to explain how such variation persists in the face of the directional selection acting on condition in house wrens and other species.
ISSN:1471-2148
1471-2148
DOI:10.1186/s12862-014-0242-8