PRINCE, LINDA M. Department of Botany MRC 166, National Museum of Natural History, Smithsonian Institution, Washington, D.C. 20560. - Additional evidence of monophyly, paraphyly, and polyphyly in genera of Theaceae.
Recent investigations of DNA sequence data for representatives of
Theaceae (sensu stricto = Theoideae of Cronquist) identified several
paraphyletic or polyphyletic genera yet significant questions remained
due to taxon sampling issues and to the low level of sequence
divergence of the previously sampled DNA regions (rbcL and
matK plus partial flanking spacers). New data using nuclear
(ITS and rpb2 intron 23) and chloroplast intergenic spacer
(trnL to trnF) regions are providing increased
resolution and higher statistical support for many nodes. Despite
differences in taxon sampling, the overall topologies from separate
analyses of each of the five data sets are congruent and identify
three major clades: Stewartia + Hartia, Gordonia
(sensu lato, pro parte) + Franklinia + Schima, and close
Camellia relatives [Camellia, Polyspora,
Laplacea (sensu stricto, pro parte), Tutcheria, etc.].
Camellia relatives comprise approximately 75% of the genera
(sensu stricto) and 80% of the species in this family. The
trnL to trnF intergenic spacer provides almost the same
resolution as either of the previous chloroplast data sets in roughly
one quarter to one fifth the number of bases sequenced. The smaller
fragment is much easier to amplify from herbarium DNA samples allowing
several critical taxa to be added to the study. ITS sequence data is
being used to investigate relationships in the Hartia +
Stewartia clade. It provides moderate bootstrap support for
the monophyly of both Hartia and Stewartia. The
rpb2 intron data set is being used to address relationships in
the Camellia relatives clade. It provides moderate bootstrap
support for the monophyly of each of the Camellia relatives
thus far sampled (Camellia, Laplacea, and
Polyspora), however this remains the largest and least resolved
clade of Theaceae.
Key words: ITS, rpb2 intron 23, systematics, Theaceae, trnL-trnF intergenic spacer