Fruit Set and Seed Predation in an Ohio Population of Gentiana saponaria

Abstract

-The soapwort gentian Gentiana saponaria (Gentianaceae) occurs at only three sites in Ohio, including a population at the Louis W. Campbell State Nature Preserve in Lucas County. Seed production at this population was monitored during 5 growing seasons between 1984 and 1991. A bagging experiment demonstrated that pollinators were required for effective pollination. In 1984-1985 and 1990-1991, more than 90% of the flowers set fruit, indicating that pollinator visitation (primarily by bumblebees) did not limit fruit set. Fruit set was unusually low in 1988 (37%), perhaps due to effects of drought stress on the plants and/or their pollinators. Levels of fruit damage from insect larvae ranged from >90% in 1984-1985 to a low of 37% in 1990. Seed predators consumed the small, winged seeds and also prevented normal fruit development. Uneaten seeds within damaged fruits often appeared moldy, and dispersal by wind was unlikely. These results suggest that seed predators had a greater role in regulating seed production than did pollinators, and that this cause of mortality could contribute to a decline in the abundance of G. saponaria.