Abstract
Some gynodioecious species present not only hermaphrodite and female individuals but also gynomonoecious individuals that produce both female and perfect flowers. In a study of natural populations of Silene italica, we found that gynomonoecious individuals were common in all populations (from 13 to 39%) and that their frequency was independent of the frequency of females. No relationship was found between the number of flowers a plant produced and its sex. The majority of gynomonoecious individuals showed a low proportion of female flowers but all proportions were found. Female flowers of these individuals were well-developed flowers that set fruit as often as female flowers on pure females. The percentage fruit set was characteristic of the type of flowers (around 56% for perfect flowers and 76% for female flowers) whatever the sex of the individual plant. The determination of sex is not known but data indicate that environmental conditions could be responsible for a shift between the hermaphrodite and the gynomonoecious states rather than between the female and the gynomonoecious states.