Interaction of Inbreeding with Systematic Forces

Abstract

The systematic forces, selection, mutation, and migration, tend to drive the frequency of a in an infinite population toward some equilibrium value, q_e. Introducing finite population size into the population at equilibrium creates sampling variation around q_e. The effect in a large population may be minor, and easily recognized as sampling error. But if the population is small, sampling variation may completely obscure the very existence of q_e. If, for example, there is strong selection against aa, and a remains in the infinite population only because of recurrent mutation, q_e will be very small. In generation t of a large line, q_it will be some value close to q_e. In a small line, q_it may be very large, perhaps even 1; fixation for the allele that is at a selective disadvantage can take place.