The equivalent number of breeding adults in a population after adjusting for complicating factors, such as non-random variation in family size or stochastic fluctuation in population size.
The size of an idealized population that shows the same amount of genetic drift as the population studied. This is approximately 10,000 individuals for humans, in contrast to the census population size of 6 109.
The population size that is relevant for random genetic drift. The actual number of individuals in a population that are reproducing.
the size of an “ideal population†that would have a specified rate of increase in inbreeding or decrease in genetic diversity by genetic drift.
number of individuals contributing directly to the gene pool 2. the size of an "ideal" population with the same rate of loss of heterozygosity as the actual population. The effective population size is usually lower than the census population size (i.e. the population size measured as number of individuals). Ne of a particular population is determined by several parameters describing deviations from "ideal" conditions such as sex ratio and the variance of family size. Long-term Ne is estimated by the harmonic mean of Ne over generations. At least three different effective population sizes have been identified in literature: the inbreeding effective size, the variance effective size, and the effective size for random loss of alleles (L.Laikre & N.Ryman, Effects of intraspecific biodiversity from harvesting and enhancing natural populations, AMBIO 25(8), 1996).
the size of a hypothetical stable, randomly-mating population that would have the same rate of gene loss or increase in inbreeding as the real population (size N). As all finite populations are inbred to some degree and generally do not choose mates at random, Ne is typically 1/10N or less, particularly if fewer males breed than females.
The size of a population as reflected by its rate of inbreeding.
The average number of individuals in a population that actually contribute genes to succeeding generations. This number is generally lower than the observed, censused population size, being reduced by the following factors: 1) a higher proportion of one sex may mate; 2) some individuals will pass on more genes by having more offspring in a lifetime than others; 3) any severe past reduction in population size may result in the random loss of one or more particular genes. ( Allaby 1991)
The number of breeding individuals in a population that contribute offspring to the next generation.
The size of a genetically idealized population with which an actual population can be equated genetically.
In population genetics, the concept of effective population size Ne was introduced by the American geneticist Sewall Wright, who wrote two landmark papers on it (Wright 1931, 1938). He defined it as "the number of breeding individuals in an idealized population that would show the same amount of dispersion of allele frequencies under random genetic drift or the same amount of inbreeding as the population under consideration". It is a basic parameter in many models in population genetics.