NEGRON-ORTIZ, VIVIAN* and LINDA E. WATSON. Botany Department, Miami University, Oxford, OH. - Molecular phylogenetic of Ernodea and Erithalis (Rubiaceae): Implications for Caribbean biogeography.
Two endemic Rubiaceae genera of the Caribbean, Erithalis P.
Browne (Tribe Chiococceae) and Ernodea Swart (Tribe
Spermacoceae), are composed of four to eight species, respectively.
Each genus contains several species that appear to be single island
endemics, in addition to one widespread species that is distributed
throughout the Caribbean Basin. The pan-Caribbean species occur
sympatrically with species of restricted distribution and/or endemics,
and often are intermediate in morphology. The fruits of both genera
are fleshy, potentially bird-dispersed, and float on sea water. One
chloroplast intergenic spacer of trnF/L, and two nuclear
non-coding spacer, ITS & ETS, were sequenced and analyzed
phylogenetically for Erithalis. Analyses of the combined data
set reveal two weakly supported clades: one consisting of the
widespread species E. fruticosa and E. harrisi, and the
other clade consisting of all remaining species. The two Jamaican
endemic species, E. harrisi & E. quadrangularis, are
each placed basally in these two clades. These species occur in the
mountains, which suggests a migration to the coast and to other
islands. The ITS were sequenced for Ernodea, however the data
do not provide sufficient phylogenetic resolution with two exceptions:
E. cokeri appears to be distinct and widespread E.
littoralis appears paraphyletic. In conclusion, sequence
divergence and phylogenetic resolution are low, suggesting that both
genera are recently derived.
Key words: biogeography, Caribbean, Erithalis, Ernodea, phylogenies, Rubiaceae