Pollination mechanisms in Triadica sebifera (Euphorbiaceae) in the southeastern United States1

Abstract

Effective pollination is essential to the ability of introduced plant species to establish and spread in novel habitats. In this study we examine the pollination biology of the introduced tree species Triadica sebifera on the Gulf Coast of the United States. We assessed its potential for reproduction via autogamy, self-fertilization, wind pollination, and pollen dispersal by insects, and compared visitation by native and introduced pollinators. We found little evidence of autogamy in emasculated inflorescences, and though trees were self-compatible, protandry within inflorescences and synchrony of flowering on branch systems were effective at preventing self-fertilization. Pollen was poorly dispersed by wind, and no pollen was found on traps 8 m from source trees. Although numerous insects visited inflorescences, only bees in the families Apidae and Halictidae carried more than traces of pollen. Both the introduced honeybee, Apis mellifera, and native bees carried large amounts of pollen, and native bees dominated the visitor community at three of four study sites. The results suggest that T. sebifera is primarily outcrossing and bee-pollinated, and is effectively pollinated by native generalist bees in its introduced range.