Large variance in reproductive success and the Ne/N ratio

Philip Hedrick

Research output: Contribution to journalArticlepeer-review

195 Scopus citations


The ratio of the effective population size to adult (or census) population size (Ne/N) is an indicator of the extent of genetic variation expected in a population. It has been suggested that this ratio may be quite low for highly fecund species in which there is a sweepstakes-like chance of reproductive success, known as the Hedgecock effect. Here I show theoretically how the ratio may be quite small when there are only a few successful breeders (Nb) and that in this case, the Ne/N ratio is approximately Nb/N. In other words, high variance in reproductive success within a generation can result in a very low effective population size in an organism with large numbers of adults and consequently a very low N e/N ratio. This finding appears robust when there is a large proportion of families with exactly two progeny or when there is random variation in progeny numbers among these families.

Original languageEnglish (US)
Pages (from-to)1596-1599
Number of pages4
Issue number7
StatePublished - Jul 2005


  • Conservation genetics
  • Effective population size
  • Hedgecock effect
  • N /N ratio
  • Oysters

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Genetics
  • General Agricultural and Biological Sciences


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