MOTLEY, TIMOTHY J.1* and PIERO G. DELPRETE2. 1The Lewis B. & Dorothy Cullman Program for Molecular Systematics Studies, The New York Botanical Garden, Bronx, NY 10458; 2Institute of Systematic Botany, The New York Botanical Garden, Bronx, NY 10458. - Molecular Systematics of the Chiococceae-Catesbaeeae Complex (Rubiaceae): Phylogeny and Biogeography.
The classification of the Catesbaeeae and Chiococceae tribes, along
with the entire Rubiaceae, has been intensely debated in recent years.
This debate has focused on a few key morphological characters (corolla
shape and aestivation, anther shape and position, fruit placentation,
and number and position of ovules) and one set of molecular data
(rbcL). Several phylogenetic analyses in the Rubiaceae based on
nucleotide sequences of the trnL-F and rps16 regions of the plastid
genome and the nuclear ribosomal internal transcribed spacers (ITS1&2)
suggest that none of the previously proposed classifications are
entirely correct. Molecular data suggest that the traditionally
defining flower and fruit features of the Catesbaeeae and Chiococceae
are actually phylogenetically homoplastic, leaving present generic
boundaries and relationships within the Catesbaeeae-Chiococceae
Complex in doubt. The Catesbaeeae-Chiococceae Complex is a group that
includes approximately 27 genera and 196 species primarily
concentrated in the Greater Antilles (nearly 70% of the taxa) but also
occurring in Malesia and the South Pacific (3 genera). Phylogenies
using trnL-F and rps16 have identified one major monophyletic group.
However, the ITS data provides more resolution and additional taxa
have been surveyed. Presently the ITS data is not congruent with the
other data sets and does not support the monophyly of the
Catesbaeeae-Chiococceae Complex. Additionally, Pacific genera which
have been absent in previous molecular studies have been sampled and
included in the analyses in the hope to better understand the disjunct
biogeographic distribution of these Caribbean and Pacific taxa. Based
on ITS data some genera, i.e. Exostema and Bikkia, do not appear to be
monophyletic. The Pacific taxa form two distinct clades, suggesting
that there have been apparently two separate introductions of the
Catesbaeeae-Chiococceae Complex into the Pacific basin.
Key words: Biogeography, Caribbean, Evolution, ITS, Pacific, Rubiaceae