Pollination of Viscaria vulgaris (Caryophyllaceae): The contributions of diurnal and nocturnal insects to seed set and seed predation

The contributions of diurnal and nocturnal insects to female reproductive success of the sticky catchfly Viscaria vulgaris Bernh., Caryophyllaceae, was studied in SW Sweden. Viscaria flowers produced nectar and were visited by insects for 24 hours a day. However, 90.5% of all visitors were diurnal and visitation rate at noon was 2.5 times higher than at night. Inflorescences were experimentally exposed to insects in one of four ways: four hours at noon, four hours at night, 24 hours a day, and entirely excluded from insect visits. Day-exposed flowers produced 1.8 times more seed than did night-exposed flowers. Flowers open to pollination 24 hours a day had a higher seed set than day-exposed flowers only in one of three years, and night-exposed flowers set more seeds than bagged flowers in two of three years. Seed set of all treatments declined throughout the season. Ovipositing insects, whose larvae feed on Viscaria seeds, were active at night, resulting in high predation on seeds from flowers exposed to insects for 24 hours a day and at night.