Both selection and drift drive the spatial pattern of adaptive genetic variation in a wild mammal

Derek Kong Lam, Alain C. Frantz, Terry Burke, Eli Geffen, Simon Yung Wa Sin*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


The major histocompatibility complex (MHC) has been intensively studied for the relative effects of different evolutionary forces in recent decades. Pathogen-mediated balancing selection is generally thought to explain the high polymorphism observed in MHC genes, but it is still unclear to what extent MHC diversity is shaped by selection relative to neutral drift. In this study, we genotyped MHC class II DRB genes and 15 neutral microsatellite loci across 26 geographic populations of European badgers (Meles meles) covering most of their geographic range. By comparing variation of microsatellite and diversity of MHC at different levels, we demonstrate that both balancing selection and drift have shaped the evolution of MHC genes. When only MHC allelic identity was investigated, the spatial pattern of MHC variation was similar to that of microsatellites. By contrast, when functional aspects of the MHC diversity (e.g., immunological supertypes) were considered, balancing selection appears to decrease genetic structuring across populations. Our comprehensive sampling and analytical approach enable us to conclude that the likely mechanisms of selection are heterozygote advantage and/or rare-allele advantage. This study is a clear demonstration of how both balancing selection and genetic drift simultaneously affect the evolution of MHC genes in a widely distributed wild mammal.

Original languageEnglish
Pages (from-to)221-238
Number of pages18
JournalEvolution; international journal of organic evolution
Issue number1
StatePublished - Jan 2023


  • European badgers
  • balancing selection on supertype
  • genetic diversity
  • genetic drift
  • major histocompatibility complex
  • pathogen-mediated selection


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