Genetic rescue of an insular population of large mammals

John T. Hogg, Stephen H. Forbes, Brian M. Steele, Gordon Luikart

Research output: Contribution to journalArticlepeer-review

185 Scopus citations

Abstract

Natural populations worldwide are increasingly fragmented by habitat loss. Isolation at small population size is thought to reduce individual and population fitness via inbreeding depression. However, little is known about the time-scale over which adverse genetic effects may develop in natural populations or the number and types of traits likely to be affected. The benefits of restoring gene flow to isolates are therefore also largely unknown. In contrast, the potential costs of migration (e.g. disease spread) are readily apparent. Management for ecological connectivity has therefore been controversial and sometimes avoided. Using pedigree and life-history data collected during 25 years of study, we evaluated genetic decline and rescue in a population of bighorn sheep founded by 12 individuals in 1922 and isolated at an average size of 42 animals for 10-12 generations. Immigration was restored experimentally, beginning in 1985. We detected marked improvements in reproduction, survival and five fitness-related traits among descendants of the 15 recent migrants. Trait values were increased by 23-257% in maximally outbred individuals. This is the first demonstration, to our knowledge, of increased male and female fitness attributable to outbreeding realized in a fully competitive natural setting. Our findings suggest that genetic principles deserve broader recognition as practical management tools with near-term consequences for large-mammal conservation.

Original languageEnglish
Pages (from-to)1491-1499
Number of pages9
JournalProceedings of the Royal Society B: Biological Sciences
Volume273
Issue number1593
DOIs
StatePublished - Jun 22 2006

Keywords

  • Conservation genetics
  • Genetic rescue
  • Immigration
  • Mammals

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