Natural selection acts on Atlantic salmon major histocompatibility (MH) variability in the wild

Elvira de Eyto, Philip McGinnity, Sofia Consuegra, Jamie Coughlan, Jarle Tufto, Killian Farrell, Hendrik-Jan Megens, William Jordan, Tom Cross, Rene Josephus Maria Stet

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    Abstract

    Pathogen-driven balancing selection is thought to maintain polymorphism in major histocompatibility (MH) genes. However, there have been few empirical demonstrations of selection acting on MH loci in natural populations. To determine whether natural selection on MH genes has fitness consequences for wild Atlantic salmon in natural conditions, we compared observed genotype frequencies of Atlantic salmon (Salmo salar) surviving in a river six months after their introduction as eggs with frequencies expected from parental crosses. We found significant differences between expected and observed genotype frequencies at the MH class II alpha locus, but not at a MH class I-linked microsatellite or at seven non-MH-linked microsatellite loci. We therefore conclude that selection at the MH class II alpha locus was a result of disease-mediated natural selection, rather than any demographic event. We also show that survival was associated with additive allelic effects at the MH class II alpha locus. Our results have implications for both the conservation of wild salmon stocks and the management of disease in hatchery fish. We conclude that natural or hatchery populations have the best chance of dealing with episodic and variable disease challenges if MH genetic variation is preserved both within and among populations.

    Original languageEnglish
    Pages (from-to)861-869
    Number of pages9
    JournalProceedings of the Royal Society of London. B, Biological Sciences
    Volume274
    Issue number1611
    DOIs
    Publication statusPublished - 22 Mar 2007

    Keywords

    • MHC (major histocompatibility complex)
    • natural selection
    • Atlantic salmon
    • class-II loci
    • complex variation
    • genetic-variation
    • salar l.
    • cryptococcus-neoformans
    • bacterial-infection
    • parasite resistance
    • populations
    • polymorphism
    • disease

    Cite this

    de Eyto, E., McGinnity, P., Consuegra, S., Coughlan, J., Tufto, J., Farrell, K., Megens, H-J., Jordan, W., Cross, T., & Stet, R. J. M. (2007). Natural selection acts on Atlantic salmon major histocompatibility (MH) variability in the wild. Proceedings of the Royal Society of London. B, Biological Sciences, 274(1611), 861-869. https://doi.org/10.1098/RSPB.2006.0053