Present-day Clermontia apparently represents the residuum of a relatively recent radiation from a relatively old lineage sister to the much larger genus Cyanea. Clermontia species differ dramatically in flower shape, color, and form, with several taxa having petaloid sepals. Roughly half the species are restricted to single islands, mainly Maui and Hawai`i at the young end of the Hawaiian chain. Taxa diverge little from each other in cpDNA restriction site or ITS sequences, and previous attempts to reconstruct phylogeny in this group have been largely unsuccessful. Here we present a well-resolved phylogeny based on a cladistic analysis of ISSR variation. As we had previously predicted, the most early divergent species among the present-day taxa is Clermontia fauriei of Kaua`i, the oldest tall island. The next species to diverge was Clermontia persicifolia, the only species restricted to O`ahu, the second oldest tall island. Our data are consistent with the origin of Clermontia on Kaua`i or some older, now eroded island, with subsequent dispersal down the chain toward younger islands. These data are also consistent with hybridization and with relatively extensive gene flow, perhaps occasioned by Clermontia’s dependence on vagile, forest-edge birds for fruit dispersal. Our phylogeny supports one, or at most two, origins of petaloid sepals, and at least one loss of this apparent homeotic mutation. Floral tube length appears to have evolved rapidly. A cladistic re-analysis of morphological data yields almost no resolution of evolutionary relationships.

Key words: adaptive radiation, biogeography, Clermontia, Cyanea, Hawaii, homeotic mutation