Age-specific effect of heterozygosity on survival in alpine marmots, Marmota marmota

Authors

  • AURÉLIE COHAS,

    1. Department of Behavioural Ecology and Evolutionary Genetics, Max Planck Institute for Ornithology, 82319 Seewiesen, Germany,
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  • CHRISTOPHE BONENFANT,

    1. Unité Propre de Recherche 1934, Centre d’Études Biologiques de Chizé, Centre National de la Recherche Scientifique, 79360 Beauvoir-sur-Niort, France,
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  • BART KEMPENAERS,

    1. Department of Behavioural Ecology and Evolutionary Genetics, Max Planck Institute for Ornithology, 82319 Seewiesen, Germany,
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  • DOMINIQUE ALLAINÉ

    1. Laboratoire Biométrie et Biologie Évolutive, UMR CNRS 5558, Université de Lyon, Université Claude Bernard Lyon 1, 69622 Villeurbanne CEDEX, France
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Aurélie Cohas, Fax: 33-4-72431388; E-mail: cohas@univ-lyon1.fr

Abstract

The fitness consequences of heterozygosity and the mechanisms underpinning them are still highly controversial. Using capture–mark–recapture models, we investigated the effects of individual heterozygosity, measured at 16 microsatellite markers, on age-dependent survival and access to dominance in a socially monogamous mammalian species, the alpine marmot. We found a positive correlation between standardized multilocus heterozygosity and juvenile survival. However, there was no correlation between standardized multilocus heterozygosity and either survival of older individuals or access to dominance. The disappearance of a significant heterozygosity fitness correlation when individuals older than juveniles are considered is consistent with the prediction that differences in survival among individuals are maximal early in life. The lack of a correlation between heterozygosity and access to dominance may be a consequence of few homozygous individuals attaining the age at which they might reach dominance. Two hypotheses have been proposed to explain heterozygosity-fitness correlations: genome-wide effects reflected by all markers or local effects of specific markers linked to genes that determine fitness. In accordance with genome-wide effects of heterozygosity, we found significant correlations between heterozygosities calculated across single locus or across two sets of eight loci. Thus, the genome-wide heterozygosity effect seems to explain the observed heterozygosity-fitness correlation in the alpine marmot.

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