Drift and mutation with a finite number of allelic states.

The frequencies with which alleles are alike within (Q) and between (q) populations are formulated for monoecious populations undergoing drift and mutation with unequal mutation rates among alleles for a finite number (k) of allelic states. The effective number of alleles and an application to Nei's measure of genetic distance [Nei, M. (1972) Am. Nat. 106, 283-292] are also considered for this model. The equilibrium values of Q and q increase as k decreases. Unequal mutation rates further increase the equilibrium values and reduce the rates of approach of Q and q to these values. The transitional values of Q and q are very dependent on the initial population frequency composition when mutation rates are unequal. Reducing k, of course, reduces the effective number of alleles, which is further reduced by unequal mutation rates. Complications introduced by initial population composition, unequal mutation rates, and number of allelic states, coupled with data limitations for long-term measures of genetic distance or population differentiation, with mutation as the main driving force, are discussed.