THE RELATIONS BETWEEN POPULATION STRUCTURE AND RATE OF INBREEDING.

Abstract

Historically, the theory and practice of population genetics has been based on either the assumption that in natural populations generations are discrete or that they overlap continuously. Neither of these assumptions provides an accurate representation of the structure of most populations. Charlesworth and Giesel ( 1971 ) have shown that the age structure of a population which has overlapping generations and discrete age classes can have important effects on the course of natural selection and on the genetic structure of such populations and that the field results of many evolutionists might be profitably reinterpreted on the basis of age distributed selection. Recently, Levin et al. (1969) calculated the effective deme size of some populations of Mus musculus using the common discrete generation definition. It is likely that their interpretation of their results would have been significantly different had they considered the age distribution of their populations. Nei (pers. comm.) feels tentatively that discrete generation definitions of effective size should be adequate for most population types. In this paper, I show that effective size is an important function of the age distribution of the population and that, because of this, evolutionary biologists who are concerned with small natural populations should consider the population's breeding structure in their analyses of the genetics of the populations. Rates of inbreeding in randomly mating populations characterized by overlapping generations and discrete age classes, and age specific fecundity are investigated using