Abstract
A single‐sex model is presented that calculates the probability of detecting multiple mating ( PrDM ) given genetic data from the single genetic parent and a sample of its offspring. The model incorporates the effects of numbers of loci, alleles, offspring and genetic parents contributing to the multiple mating, all of which effect PrDM . The model is used to determine the actual number of loci and offspring that are required to detect multiply mated broods with high probability (80 and 95%). For example, if two sires contribute with equal fertilization success to multiply mated broods, then only 10 offspring and one locus with seven equally common alleles are required to ensure that 80% of multiple mated broods are detected. Ninety‐five per cent of multiple mated broods can be detected with 10 offspring and five loci with four equally common alleles. The utility of the model is demonstrated with biological examples addressing geographic variation in multiple paternity among natural populations of guppies Poecilia reticulata and mosquitofish Gambusia holbrooki .