The effective population size of some age-structured populations

It was shown in a previous paper that if generations are discrete, then the effective population size of a large population can be derived from the th eory of multitype branching processes. It turns out to be proportional to t he reciprocal of a term that appears in the denominator of expressions for survival probabilities when there is a supercritical positively regular bra nching process for which the dominant positive eigenvalue of the first mome nt matrix is slightly larger than 1. If there is an age-structured populati on with unchanging proportions among sexes and age groups, then the effecti ve population size is shown to he also obtainable from the theory of multit ype branching processes. The expression for this parameter has the same for m as in the corresponding model for discrete generations, multiplied by an appropriate measure of the average length of a generation. Results are obta ined for dioecious random mating populations, populations reproducing partl y by selfing, and populations reproducing partly by full-sib mating. (C) 20 00 Elsevier Science Inc. All rights reserved.