ESSIG, FREDERICK B.*, JAMES R. GAREY, AND JONATHAN M. SLOMBA. Department of Biology - SCA 110, University of South Florida, Tampa, FL 33620. - The infrageneric classification of Clematis (Ranunculaceae).
The infrageneric classification of the large, cosmopolitan genus,
Clematis (Ranunculaceae), has been based on minor differences
in vegetative and inflorescence morphology, along with flower size,
shape and color. The most comprehensive global classification
recognizes 26 infrageneric taxa, including the sometimes segregated
genera Archiclematis, Naravelia and Clematopsis,
but many of the 250-300 species are uncertainly placed or unplaced
within this system. A more sound basis for classification, based on
seedling morphology, reproductive compatibility, and a reevaluation of
a number of vegetative and floral characters, was suggested by earlier
work. A major feature of a new classification would be the division
of at least the bulk of the genus into two subgenera, one exhibiting
classical epigeal germination and alternate seedling phyllotaxy, and
the other exhibiting a type of hypogeal germination and opposite
seedling phyllotaxy. The proposed major divisions of the genus are
being tested with a phylogenetic study based on DNA sequence data,
which will be expanded as part of the development of a comprehensive
new classification. We have so far extracted DNA from 18 taxa broadly
representative of the genus and are PCR amplifying the nuclear
ribosomal RNA internal spacer and a noncoding region located between
the trnT and trnF genes of the chloroplast genome. Preliminary
results of that study will be presented.
Key words: classification, Clematis, DNA, infrageneric, Ranunculaceae