Gene flow-change in gene pool due immigration or emmigration of individuals between populations. Usually not adaptive. Mutation-change in allele frequency due to net mutation. Usually not adaptive. In the long run, however, it is the original source of genetic variation for natural selection.
Large populations reduce the effect of mutations.
Nonrandom mating-interbreeding or selection of mates for specific phenomenon. Reduces heterosygous individuals. Natural selection- differential reproductive success increases the frequency of some alleles over others. Non-adaptive is not the same as maladaptive. V. Convergent evolution.