Inbreeding and outbreeding

Katherine Ralls, Richard Frankham, Jonathan D. Ballou

Research output: Chapter in Book/Report/Conference proceedingEntry for encyclopedia/dictionary/reference book

6 Citations (Scopus)


Inbreeding refers to mating of related individuals. It results in a decline in survival and reproduction (reproductive fitness), known as inbreeding depression, in most species of plants and animals. Outbreeding refers to matings between individuals from different populations, subspecies, or species. Outbreeding can result in a decline in reproductive fitness known as outbreeding depression, but this is less common than inbreeding depression. Inbreeding in small populations typically increases extinction risk, especially for species that do not normally inbreed. Outbreeding between populations with chromosomal incompatibilities or those that are adapted to different environmental conditions can also increase extinction risk. Restoring gene flow between isolated populations can reverse inbreeding depression. This article discusses the conservation implications of inbreeding and outbreeding depression.
Original languageEnglish
Title of host publicationEncyclopedia of biodiversity
EditorsSimon A Levin
Place of PublicationAmsterdam, The Netherlands
Number of pages8
ISBN (Print)9780123847195
Publication statusPublished - 2013


  • Extinction
  • Fitness
  • Genetic diversity
  • Heterozygosity
  • Inbreeding
  • Inbreeding depression
  • Lethal equivalents
  • Outbreeding
  • Outbreeding depression


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