HARDY, CHRISTOPHER R.1,2*, JERROLD I DAVIS1, ROBERT B. FADEN3, and DENNIS W. STEVENSON1,2. 1Bailey Hortorium, Cornell University, Ithaca, NY 14853; 2New York Botanical Garden, Bronx, NY 10458; 3Department of Botany, National Museum of Natural History, Smithsonian Institution, Washington, DC 20560. - Phylogenetics of Cochliostema, Geogenanthus, and an undescribed genus (Commelinaceae) using morphology and DNA sequence data from 26S, 5S-NTS, rbcL, and trnL-F loci.
A phylogenetic study was conducted on a group of three small genera of
neotropical Commelinaceae that exhibit a variety of unusual floral
morphologies and habits. Morphological characters and DNA sequence
data from plastid (rbcL, trnL-F) and nuclear ribosomal
(5S-NTS, partial 26S) loci were used. In separate analyses, 26S and
rbcL character sets each yielded cladograms that were equally
or more fully resolved than those from analyses of the more
rapidly-evolving 5S-NTS and trnL-F loci. Analysis of the
molecular character sets, in combination with morphological
characters, has provided a framework for the study of life form and
morphological character evolution. Our studies indicate that the
unusual spirally-coiled anthers and other apparent autapomorphies in
the flowers of Cochliostema are elaborations of developmental
synapomorphies shared by Cochliostema with Geogenanthus
and an undescribed genus. The adaptations associated with the
epiphytic habit of Cochliostema are best understood in light of
their similarity to homologous features in the undescribed genus. Our
inclusion in this study of two undescribed plesiomorphic species of
Geogenanthus has revealed an evolutionary trend towards
reduction in the inflorescence in this genus.
Key words: Cochliostema, Commelinaceae, Geogenanthus, ribosomal DNA