Contemporary selection on MHC genes in a free-living ruminant population

Wei Huang, Kara Dicks, Jarrod D. Hadfield, Susan Johnston, Keith Ballingall, Josephine M Pemberton

Research output: Contribution to journalArticlepeer-review

Abstract

Genes within the major histocompatibility complex (MHC) are the most variable identified in vertebrates. Pathogen-mediated selection is believed to be the main force maintaining MHC diversity. However, relatively few studies have demonstrated contemporary selection on MHC genes. Here, we examine associations between MHC variation and several fitness measurements including total fitness and five fitness components, in 3400 wild Soay sheep (Ovis aries) monitored between 1989 and 2012. In terms of total fitness, measured as lifetime breeding success of all individuals born, we found haplotypes named C and D were associated with decreased and increased male total fitness respectively. In terms of fitness components, juvenile survival was associated with haplotype divergence while individual haplotypes (C, D and F) were associated with adult fitness components. Consistent with the increased male total fitness, the rarest haplotype D has increased in frequency throughout the study period more than expected under neutral expectations. Our results demonstrate contemporary natural selection is acting on MHC class II genes in Soay sheep and the mode of selection on specific fitness components can be different mode from selection on total fitness.
Original languageEnglish
Number of pages11
JournalEcology Letters
Early online date20 Jan 2022
DOIs
Publication statusE-pub ahead of print - 20 Jan 2022

Keywords

  • MHC
  • selection
  • soay sheep

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