An alternative approach to asymptotic results on genetic composition when the population size is varying.

This paper is concerned with methodology for studying the long-term genetic composition of a population of haploid individuals in the case where the population size is varying. A general approach requiring a minimum of assumptions is described based on constructing martingales out of expressions for the means of the numbers of allelic types, conditional on the past. Earlier investigations were based on studying the asymptotic behaviour of the proportion of alleles of a certain type in the population. Several applications demonstrate that the approach suggested in the paper provides results which usefully complement ones obtained previously.