Estimating the effective number of breeders from heterozygote excess in progeny

The heterozygote-excess method is a recently published method for estimatin g the effective population size (N-e). It is based on the following princip le: When the effective number of breeders (N-eb) in a population is small, the allele frequencies will (by chance) be different in males and females, which causes an excess of heterozygotes in the progeny with respect to Hard y-Weinberg equilibrium expectations. We evaluate the accuracy and precision of die heterozygote-excess method using empirical and simulated data sets from polygamous, polygynous, and monogamous mating systems and by using rea listic sample sizes of individuals (15-120) and loci (5-30) with varying le vels of polymorphism. The method gave nearly unbiased estimates of N-eb und er all three mating systems. However, the confidence intervals on the point estimates of N-eb were sufficiently small (and hence the heterozygote-exce ss method useful) only in polygamous and polygynous populations that were p roduced by <10 effective breeders, unless samples included > similar to 60 individuals and 20 multiallelic loci.