The Neutral Equation

According to the Neutral Theory, observed Heterozygosity (H) (average fraction of heterozygous loci per individual) is a balance between loss of variation in finite populations of size N_e and its replacement by recurrent mutation at a rate u. Then, H = (4N_eu) / (4N_eu + 1) : for example, if N_e = 10⁶ and u = 10^-7, then   H = (0.4)/(0.4 + 1) = 0.29. As is apparent in the above graph, which shows he range of observed heterozygosities bracketed  in red, few species approach this value. One interpretation is that observed population sizes typically overestimates the effective population size.

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Text material © 2005 by Steven M. Carr

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