GIVNISH, THOMAS J.*, GREG BEAN, AND KENNETH J. SYTSMA. Department of Botany, University of Wisconsin, Madison, WI 53706. - Phylogeny, floral evolution, and patterns of inter-island dispersal in Clermontia (Lobeliaceae) in Hawaii based on ISSR variation.
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