Advantages of Being a Specialist Female in Nodioecious Silene Vulgaris S.L. (Caryophyllaceae)

According to sex allocation theory, to maintain a mutant male‐sterile plant in a population of hermaphrodites such a plant must compensate its loss of fitness caused by inhibition of pollen production with a higher reproductive success through its female function. In the present study of a gynodioecious population of Silene vulgaris (Caryophyllaceae) I show that hermaphrodites not only benefit from outcrossing, in that progeny from outcrossed flowers are more vigorous than those from selfed flowers within an individual plant, but they also suffer heavily from self‐pollination between different flowers of the same individuals, which could be demonstrated in experimentally made male‐sterile (emasculated) individuals. Seeds from the emasculation period were heavier and germinated better than when the same individual was an intact hermaphrodite. Naturally male‐sterile (female) individuals produced more fruits due to flowers staying open longer for pollen to arrive via some vector. However, the higher seed number alone could not provide the fitness advantage needed for females to be maintained in the population, but females also produced heavier seeds as compared to the hermaphrodites. Differences in seed survival and seedling establishment in the field are expected to add the advantages necessary for female plants to be selectively plausible.