The deterministic behavior of self-incompatibility alleles.

For a system of n self-incompatibility alleles, neglecting mutation and random drift, it is shown that the completely symmetric equilibrium is locally stable, and any allelic frequency less than q equals 1 + a minus the square root of 1 + a-2, where a equals [2(n minus 1)]- minus 1, will increase. For all n, q greater than (2n)- minus 1, but if n greater than 1, q is approximately equal to (2n)- minus 1.