RESUMO
In this paper an analysis is made of a model of selection for asexual reproduction in hermaphrodite (or monoecious) populations in which variation occurs in relative female and male fertilities. It is shown that the advantage of an asexual mutant (the cost of sex) increases with increasing degree of differentiation in functional sex. This effect is very marked at low levels of selfing, but weak with a high selfing rate. In general, the advantage of an asexual mutant in a hermaphrodite population depends on the relative resource allocation to male and female gametes, and increases with increasing bias to femaleness. Thus the cost of sex in gynodioecious populations is (with a low level of selfing) as high as in a dioecious population. This applies, however, to a nuclear genetic determination of gynodioecy, which is presumably rare. In a more realistic model assuming nuclear-cytoplasmic determination of gynodioecy the cost of sex is considerably lower.
