THE EFFECT OF MATING STRUCTURE AND PROGENY DISTRIBUTION ON HETEROZYGOSITY VERSUS THE NUMBER OF ALLELES AS MEASURES OF VARIATION

Heterozygosity and the number of alleles are both measures of the gene tic variation of a population. They are qualitatively similar if the d istribution of the number of progeny is Poisson, but not necessarily f or other distributions. In particular, selfing decreases heterozygosit y and also decreases the number of alleles when the progeny distributi on is Poisson, but decreases heterozygosity and increases the number o f alleles when there are two progeny per individual. This is because h eterozygosity is closely related to the breeding structure (inbreeding ) of the population, whereas the number of alleles is more influenced by the variation of the sampling process. Branching processes are empl oyed to model the dynamics of mutant alleles, with drift and subsequen t mutation contributing to extinction. In populations of four individu als, double first cousin mating has greater heterozygosity, but fewer alleles, than half-sib mating. (C) 1995 Academic Press Limited