Functional specialization for pollination by scoliid wasps and solitary bees of Ampelopsis glandulosa (Vitaceae)

Abstract

The insect visitors to the flowers of Ampelopsis glandulosa (Vitaceae) were surveyed in western Japan. This plant species has cymose inflorescences with many greenish open flowers that contain copious nectar. Diverse insect species visit the flowers and the number of wasps was greater than that of bees. The most frequent visitor at all study sites was the scoliid wasp Scolia oculata. Solitary halictine and andrenid bees were also relatively frequent visitors at some sites. Because a large amount of yellow pollen from A. glandulosa was attached to the bodies of both wasps and bees, they were considered to be effective pollinators. Although honey-bees and vespid wasps were also frequent visitors at many sites, a negligible amount of yellow pollen was found to be attached to the bodies of a majority of these; therefore, they were not considered to be effective pollinators. Vespid wasps are predators of herbivorous insects and observations revealed that they are nectar thieves of A. glandulosa. Because diverse insects were attracted to A. glandulosa flowers, these flowers appear to be generalists, however, only short-tongued scoliid wasps, halictine bees, and andrenid bees appeared to be effective pollinators. These results therefore suggest that A. glandulosa is functionally specialized for short-tongued hymenopteran pollinators. This study adds to a growing body of work on specialized wasp pollination, a system hitherto mostly known from South Africa.