The Effect of Nectar-Thieving Ants on the Reproductive Success of Frasera speciosa (Gentianaceae)

Abstract

The impact of nectar-thieving ants on the reproductive success of Frasera speciosa (Gentianaceae), a perennial monocarp with periodic, synchronous flowering, was studied in a Wyoming alpine meadow. Plants from which ants were excluded had higher rates of flower visitation by other insects, and higher standing crops of nectar, than did plants visited by ants. However, there were no significant differences in either seed set or seed predation in plants with and without ants. The lack of effect of ants upon the reproductive success of Frasera may be due in part to temporal separation of the activities of ants and some important pollinators and seed predators. However, the abundant nectar produc- tion, large inflorescences and low rates of seed predation in Frasera, which are all related to its habit of periodic synchronous flowering, may reduce the effects of nectar-thieving ants upon the species.