MOLECULAR PHYLOGENETIC ANALYSIS OF THE HAWAIIAN ENDEMICS SCHIEDEA ANDALSINIDENDRON (CARYOPHYLLACEAE)

Schiedea and Alsinidendron (Caryophyllaceae), which represent the fift h or sixth largest endemic radiation of species in the angiosperm flor a of the Hawaiian Islands, exhibit striking diversity in morphology, b reeding system, and habitat. To gain a historical perspective on this diversity, we conducted a phylogenetic analysis using restriction site variation in chloroplast DNA and nuclear ribosomal DNA. In addition, we compared, and ultimately combined, the molecular data with a recent ly published morphological data set. Within the Schieden-Alsinidendron lineage, DNA variation is limited, and relationships are generally po orly resolved. These results raise the possibility that, following the initial colonization of the Hawaiian archipelago and the early divers ification of the complex, much of the complex radiated rapidly and rel atively recently. Phylogenetic analyses of DNA data revealed three cla des within the complex (the S. membranacea, S. nuttallii, and S. adama ntis clades), in agreement with results of a morphologically-based ana lysis. Molecular data do not, however, support the S. globosa clade, a weakly-supported clade based on morphology. A combined analysis of mo rphological and molecular data provided both greater resolution and st ronger internal support than either data set did individually. The mol ecular and combined topologies suggest nearly identical patterns of th e evolution of sexual dimorphism, habitat shifts, and biogeography wit hin the complex. However, the greater resolution in trees derived from the combined analysis suggests simpler patterns of breeding-system ev olution and habitat shifts. Sexual dimorphism may have evolved twice i n the complex, with a single reversal to hermaphroditism in one specie s, or perhaps only once, with three reversals to hermaphroditism. Alth ough the habitat occupied by the ancestor of the complex remains uncer tain, it appears that a single shift to dry habitats more or less acco mpanied the evolution of dimorphic breeding systems, followed by a sin gle shift back to a mesic environment in one species. Alternatively, t wo parallel shifts to dry habitats may have occurred. Molecular data a re consistent with an origin on Kaua'i of the S. membranacea, S. adama ntis, and S. nuttallii clades, as suggested by previous morphological analyses. However, both the molecular and combined trees suggest it is equally likely that the complex originated on O'ahu.