Nectar content differences between the genders of the bladder campion, Silene vulgaris

TitleNectar content differences between the genders of the bladder campion, Silene vulgaris
Publication TypeJournal Article
Year of Publication1986
AuthorsJolls CL, Hatley CL
JournalAssociation of Southeastern Biologists Bulletin

Theory suggests that females are at a disadvantage compared to hermaphrodites in a gynodioecious species. Females contribute genes only as maternal parents through seed set, while hermaphrodites set seed and function as pollen parents in self- or cross-fertilization. Females may be maintained in populations by having reproductive output greater than that of bisexuals. This study is part of a larger empirical effort to document the relative reproductive success of hermaphrodites and females of Silene vulgaris. We have reported previously, contrary to prediction, greater reproductive output in hermaphrodites; however, a greater proportion of female flowers set fruit. The present study investigated this differential fruit set by comparing attractiveness of the two genders, measured as nectar content. Although data from a hand refractometer showed no significant difference in sugar content between the genders (15.5% +/- .85 vs. 14.4% +/- .41), use of a spectrophotometric assay for minute quantities of sugar revealed significantly more total rinsable sugar in the nectaries of hermaphrodites compared to females (.938 mg +/- .105 vs. .515 +/- .09). Nectar sugar content changed in both genders through time, peaking at stigma receptivity. Neither of the genders appear to be preferentially visited by pollinators, therefore, we hypothesize that the greater fruit set in females is due to genetic factors such as reduced inbreeding depression rather than differential attractiveness and pollinator visitation.