XVI International Botanical Congess

Hawaiian Psychotria are often cited as an insular shift from hermaphroditism to dicliny, and one of six known cases where dioecy may have evolved from distyly. We re-examined the hypothesis that dioecy evolved from distyly in Hawaiian Psychotria, based on field studies and reconstruction of character-state evolution using a molecular phylogeny. Our data suggest that Hawaiian Psychotria are monophyletic and sister to taxa from the western Pacific. The Hawaiian species are either hermaphroditic or gynodioecious. It appears unlikely that dicliny in the Hawaiian clade arose from distyly, and we infer ancestral breeding systems to have been hermaphroditic or gynodioecious. The evolution of breeding systems in insular Psychotria appears to be more complex than previously thought.