Impact of historical founder effects and a recent bottleneck on MHC variability in Commander Arctic foxes (Vulpes lagopus)

Authors

  • Anna I. Ploshnitsa,

    1. Department of Vertebrate Zoology, Lomonosov Moscow State University, 1/12 Leninskie gory, 119991 Moscow, Russia
    2. Evolutionary Genetics, Leibniz Institute for Zoo and Wildlife Research (IZW), D-10315 Berlin, Germany
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  • Mikhail E. Goltsman,

    1. Department of Vertebrate Zoology, Lomonosov Moscow State University, 1/12 Leninskie gory, 119991 Moscow, Russia
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  • David W. Macdonald,

    1. Wildlife Conservation Research Unit, Department of Zoology, University of Oxford, The Recanati-Kaplan Centre, Tubney House, Tubney, OX13 5QL Oxon, UK
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  • Lorna J. Kennedy,

    1. Centre for Integrated Genomic Medical Research, University of Manchester, M13 9PT Manchester, UK
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    • These authors are joint senior authors.

  • Simone Sommer

    1. Evolutionary Genetics, Leibniz Institute for Zoo and Wildlife Research (IZW), D-10315 Berlin, Germany
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    • These authors are joint senior authors.


Anna I. Ploshnitsa, Lomonosov Moscow State University, Biology Faculty, Department of Vertebrate Zoology, 1/12 Leninskie gory, 119991 Moscow, Russia. Tel: 07758049705; Fax: +74959394309; E-mail: ploshnitsa@gmail.com
Funded by a grant from the Peoples Trust for Endangered Species to DWM, the DAAD Leonard-Euler (A08/01104 and 50077303), Sigma-Xi, Grants-in-Aid (G200631112503926), the Russian Foundation for Basic Research (07-04-007-45a), and the Leibniz Institute for Zoo and Wildlife Research, Berlin.

Abstract

Populations of Arctic foxes (Vulpes lagopus) have been isolated on two of the Commander Islands (Bering and Mednyi) from the circumpolar distributed mainland population since the Pleistocene. In 1970–1980, an epizootic outbreak of mange caused a severe population decline on Mednyi Island. Genes of the major histocompatibility complex (MHC) play a primary role in infectious disease resistance. The main objectives of our study were to compare contemporary variation of MHC class II in mainland and island Arctic foxes, and to document the effects of the isolation and the recent bottleneck on MHC polymorphism by analyzing samples from historical and contemporary Arctic foxes. In 184 individuals, we found 25 unique MHC class II DRB and DQB alleles, and identified evidence of balancing selection maintaining allelic lineages over time at both loci. Twenty different MHC alleles were observed in mainland foxes and eight in Bering Island foxes. The historical Mednyi population contained five alleles and all contemporary individuals were monomorphic at both DRB and DQB. Our data indicate that despite positive and diversifying selection leading to elevated rates of amino acid replacement in functionally important antigen-binding sites, below a certain population size, balancing selection may not be strong enough to maintain genetic diversity in functionally important genes. This may have important fitness consequences and might explain the high pathogen susceptibility in some island populations. This is the first study that compares MHC diversity before and after a bottleneck in a wild canid population using DNA from museum samples.

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