A deterministic two-allele model is presented for the evolutionary dyn
amics of deleterious mutations selected in the male gametophytic stage
of a population with mixed selfing and random mating. The equilibrium
frequency of the deleterious allele increases with the selfing rate,
and the deleterious allele will be fixed, if the selfing rate is suffi
ciently high and mutation is unidirectional. The effect of pollen sele
ction decreases as the selfing rate increases. Some consequences of ma
le gametophytic selection for the evolution of mating systems are disc
ussed.