section_path: Reproductive systems/Inbreeding
section_name: Inbreeding
paragraph_text: Inbreeding
  
  During sexual reproduction, mating with a close relative (inbreeding) often leads to inbreeding depression. Inbreeding depression is considered to be largely due to expression of deleterious recessive mutations. The effects of inbreeding have been studied in many vertebrate species.
  
  In several species of fish, inbreeding was found to decrease reproductive success.
  
  Inbreeding was observed to increase juvenile mortality in 11 small animal species.
  
  A common breeding practice for pet dogs is mating between close relatives (e.g. between half- and full siblings). This practice generally has a negative effect on measures of reproductive success, including decreased litter size and puppy survival.
  
  Incestuous matings in birds result in severe fitness costs due to inbreeding depression (e.g. reduction in hatchability of eggs and reduced progeny survival).