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BMC Evolutionary Biology

, 15:242

Evolutionary ecology and behaviour


BackgroundA multitude of correlations between heterozygosity and fitness proxies associated with disease have been reported from wild populations, but the genetic basis of these associations is unresolved. We used a longitudinal dataset on wild Galapagos sea lions Zalophus wollebaeki to develop a relatively new perspective on this problem, by testing for associations between heterozygosity and immune variation across age classes and between ecological contexts.

ResultsHomozygosity by locus was negatively correlated with serum immunoglobulin G production in pups 0–3 months of age, suggesting that reduced genetic diversity has a detrimental influence on the early development of immune defence in the Galapagos sea lion. In addition, homozygosity by locus was positively correlated with total circulating leukocyte concentration in juveniles 6–24 months of age, but only in a colony subject to the anthropogenic environmental impacts of development, pollution and introduced species, which suggests that reduced genetic diversity influences mature immune system activity in circumstances of high antigen exposure.

ConclusionsThese findings demonstrate the environmental context-dependency of the phenotypic expression of immune variation, which is implicit in the theory of ecoimmunology, but which has been rarely demonstrated in the wild. They also indicate that heterozygosity may be linked to the maintenance of heterogeneity in mammalian immune system development and response to infection, adding to the body of evidence on the nature of the mechanistic link between heterozygosity and fitness.

KeywordsGenetics Microsatellite Inbreeding Immunity Immunoglobulin Leukocyte Life history Pinniped Zalophus wollebaeki Galapagos AbbreviationsMLHMulti-locus heterozygosity

HFCHeterozygosity-fitness correlations

IgGImmunoglobulin G

HWEHardy-Weinberg equilibrium

HLHomozygosity weighted by locus

GLMGeneralised linear model

GLMMGeneralised linear mixed model

SEStandard error

SDStandard deviation

LRTLikelihood ratio test

Electronic supplementary materialThe online version of this article doi:10.1186-s12862-015-0519-6 contains supplementary material, which is available to authorized users.

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Autor: Patrick M. Brock - Simon J. Goodman - Ailsa J. Hall - Marilyn Cruz - Karina Acevedo-Whitehouse


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