PHYLOGENETIC POSITION OF THE HAWAIIAN GERANIUMS BASED ON RBCL SEQUENCES

The seven currently recognized species of Geranium endemic to the Hawa iian Islands are unusual in their shrubby or arborescent habit and unl obed, parallel-veined leaves rather than the palmately cleft or lobed leaves and herbaceous habit typical of the genus. Their placement with in the genus and their biogeographic source have been obscured by this morphological distictiveness and the limited resolution of relationsh ips on the basis of morphology in the very speciose subgenus Geranium. Phylogenetic analysis of rbcL gene sequences provides strong support for the monophyly of the Hawaiian group, and indicates that the Hawaii an clade is deeply nested within section Geranium rather than comprisi ng a separate section. The continental relatives studied to date with the greatest similarity in sequence to the Hawaiian group are native t o the Americas rather than Asia or the Pacific. The Hawaiian species a re extremely similar to one another in rbcL sequence, while the tree t opology obtained is consistent with a basal position for Geranium arbo reum within the group.