Genetic and Environmental Variation in Condition, Cutaneous Immunity, and Haematocrit in House Wrens
Document Type
Article
Publication Title
BMC Evolutionary Biology
Publication Date
Winter 12-4-2014
Keywords
Animal model, Condition, Haematocrit, Heritability, Genetic variation, Immunity, Life-history theory, PHA, Troglodytes aedon
Abstract
Background
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.
Results
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.
Conclusions
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.
Funding Source
Financial support was provided by NSF grants GK12-0086354, IBN-0316580, IOS-0718140 and IOS-1118160; NIH grant R15HD076308-01; a visiting professorship from the Leverhulme Trust (SKS); the School of Biological Sciences, Illinois State University; a BBSRC David Phillips Research Fellowship (AJW); and student-research grants from the Beta Lambda Chapter of the Phi Sigma Biological Sciences Honor Society (AMF).
Recommended Citation
Sakaluk, S.K., Wilson, A.J., Bowers, E.K. et al. Genetic and environmental variation in condition, cutaneous immunity, and haematocrit in house wrens. BMC Evol Biol 14, 242 (2014). https://doi.org/10.1186/s12862-014-0242-8
DOI
10.1186/s12862-014-0242-8
Comments
First published in BMC Evolutionary Biology (2014): https://doi.org/10.1186/s12862-014-0242-8
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited.
Supplementary: http://doi.org/doi:10.5061/dryad.jk2m0