Effective Population Size

Abstract

AbstractWe expect heterozygosity to be lost at a rate of 1/2N per generation in an ideal population because of genetic drift where N is the census population size. The effective size of a population is the size of the ideal (Wright–Fisher) population that will result in the same amount of genetic drift as in the actual population being considered. Heterozygosity is generally lost at a rate much faster than 1/2N in natural populations primarily because reproductive success is much more variable than assumed in an ideal population. Therefore, the effective size of natural populations (Ne) is often much smaller than the census population size (Ne << N). Predicting the rate of loss of heterozygosity over calendar time in a population requires an estimate of both Ne and the generation interval. Genomic techniques provide a variety of methods to estimate Ne in natural populations.