Sex expression and fruit set in Silene littorea (Caryophyllaceae): variation among populations

The flowers of Silene littorea may be female or hermaphrodite, and an individual may show any of three sexual phenotypes: female-flowers-only, hermaphroditeflowers-only, or mixed-type. We estimated the relative frequencies and fruit sets of each flower type and each sexual phenotype in eleven S. littorea populations in northwest Spain. For all plants and sites combined, 18% of flowers were female and 82% hermaphrodite. Individuals either had only female flowers (6%), only hermaphrodite flowers (43%), or had both flower types (51%). The relative frequencies of female and hermaphrodite flowers, and of sexual phenotypes, vaned among populations. There was no significant effect of flower sex on its probability of setting fruit. Differences among individual plants within populations had the most prominent role in explaining variation among flowers in probability of setting fruit, while population and its interaction with flower sex had a negligible and nonsignificant influence. Mean fruit set per plant did not differ significantly between sexual phenotypes. Neither population nor its interaction with sexual phenotype accounted for significant amounts of between-plant variance in fruit set.