Selection maintains MHC diversity through a natural population bottleneck

Matthew K. Oliver*, Stuart B. Piertney

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

65 Citations (Scopus)


A perceived consequence of a population bottleneck is the erosion of genetic diversity and concomitant reduction in individual fitness and evolutionary potential. Although reduced genetic variation associated with demographic perturbation has been amply demonstrated for neutral molecular markers, the effective management of genetic resources in natural populations is hindered by a lack of understanding of how adaptive genetic variation will respond to population fluctuations, given these are affected by selection as well as drift. Here, we demonstrate that selection counters drift to maintain polymorphism at a major histocompatibility complex (MHC) locus through a population bottleneck in an inbred island population of water voles. Before and after the bottleneck, MHC allele frequencies were close to balancing selection equilibrium but became skewed by drift when the population size was critically low. MHC heterozygosity generally conformed to Hardy-Weinberg expectations except in one generation during the population recovery where there was a significant excess of heterozygous genotypes, which simulations ascribed to strong differential MHC-dependent survival. Low allelic diversity and highly skewed frequency distributions at microsatellite loci indicated potent genetic drift due to a strong founder affect and/or previous population bottlenecks. This study is a real-time examination of the predictions of fundamental evolutionary theory in low genetic diversity situations. The findings highlight that conservation efforts to maintain the genetic health and evolutionary potential of natural populations should consider the genetic basis for fitness-related traits, and how such adaptive genetic diversity will vary in response to both the demographic fluctuations and the effects of selection.

Original languageEnglish
Pages (from-to)1713-1720
Number of pages8
JournalMolecular Biology and Evolution
Issue number7
Early online date9 Feb 2012
Publication statusPublished - Jul 2012


  • adaptive evolution
  • balancing selection
  • random genetic drift
  • conservation genetics
  • major histocompatibility complex
  • vole Arvicola-terrestris
  • genetic diversity
  • water vole
  • evolution
  • loci
  • differentiation
  • polymorphism
  • survival


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