Systematics Section / ASPT
Neubig, K. M. , Williams, N. H. , Whitten, W. M. , Pupulin, F. .
Molecular systematics of the genus Dichaea (Zygopetalinae: Orchidaceae).
THE genus Dichaea, with over 100 species found throughout the Neotropics, is easily recognized by distichous leaves on long stems without pseudobulbs and flowers with infrastigmatic ligules. The genus has traditionally been divided taxonomically into four sections based primarily on presence/absence of muricate ovaries and presence/absence of an abscission layer in the leaves (where the sheath meets the blade). Sequence data of the ITS, matK and trnL-trnF regions were used to estimate the phylogeny of Dichaea. Each of the four sections was sampled, with the greatest sampling in section Dichaea, the most diverse and speciose group. Molecular and morphological data support Dichaea as a monophyletic genus. According to molecular data, section Dichaeopsis is paraphyletic and based on symplesiomorphic features such as leaves with an abscission layer and smooth ovaries (which are both commonly found in the Orchidaceae). Section Pseudodichaea is a monophyletic group defined by having muricate ovaries and leaves with an abscission layer, but its placement is uncertain within the genus. Together sections Dichaeastrum and Dichaea form a monophyletic group, supported by pendent habit and persistent leaves. However, section Dichaeastrum, differentiated from section Dichaea primarily by a glabrous ovary, is potentially polyphyletic within section Dichaea. The loss of an abscission layer in the leaves is a synapomorphy uniting sections Dichaea and Dichaeastrum, but is not phylogenetically informative for the other sections. The muricate ovary is a homoplasious, derived character with several losses and gains within the genus. The focus of future work will be to delimit karyological and anatomical states of Dichaea and other taxa in Zygopetalinae.
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1 - University of Florida, Department of Botany, 220 Bartram Hall, P.O. Box 118526, Gainesville, Florida, 32611-8526, USA
2 - University of Florida, Department of Botany, Florida Museum of Natural History, P.O. Box 117800, Gainesville, Florida, 32611-7800, USA
3 - Lankester Botanical Garden, Apartado 1031-7050, Cartago, , Costa Rica
Presentation Type: Poster:Posters for Sections
Location: Auditorium/Bell Memorial Union
Date: Tuesday, August 1st, 2006
Time: 12:30 PM