Generations are assumed to be non-overlapping. We consider a haploid population divided into K parts, each of which contain N adults in any generation. These are obtained by a random sampling of the offspring of the previous generation. We assume that the probability of an adult offspring of an individual in one subpopulation being in some other subpopulation is the same small positive number, no matter what two subpopulations are considered.
If the population initially has individuals of two types, A and a, it is of interest to study approximations, if n is large, to
(1) the rate at which A or a is lost between generations n-1 and n,
(2) the probability that A and a are still present in generation n,
(3) the joint distribution of frequencies of A in the subpopulations.
A solution is given for the first problem. It is found that if the mean number of migrants per generation from one subpopulation to another is at least as large as 1, the population behaves almost as if it were not subdivided. But if this number is considerably less that 1, then the rate at which one or the other gene is lost is slower than in an undivided population. The other two problems are discussed for K = 2.