Individual-based genotype analysis in studies of parentage and population assignment: how many loci, how many alleles?

Abstract

We developed multivatiate analytical models to predict the probability of assigning offspring to parental couples as a function of population size, number of loci, and allelic diversity and the relationships between the probability of allocating individuals to their population of origin as a function of number of loci and allelic diversity. The parentage model predicts that the number of loci and number of alleles contribute interactively to increase assignment success. Given sufficient allelic diversity, a relatively low number of loci is required to achieve high allocation success even for relatively large numbers of possible parents. In contrast, the population model predicts an additive contribution of the number of loci and alleles. There appears to be no significant gain in increasing allelic diversity beyond approximately 6-10 alleles per locus in population assignment studies. Such predictive models should contribute to maximizing the returns of population and parentage assignment studies by increasing our understanding of interactions among the various variables affecting allocation success and by allowing the adjustment a priori of the required level of resolution and, consequently, optimizing the costs-benefits ratio in the use of molecular markers.