Systematics Section / ASPT
Ghebretinsae, Amanuel , Thulin, Mats , Barber, Janet C. .
Molecular phylogeny of Cucumis and related genera (Benincaseae, Cucurbitaceae).
Cucumis L. (Cucurbitaceae) is one of the economically most important genera of flowering plants, comprising 33 species of annuals and perennials that are distrbuted mainly in tropical and southern Africa and Asia. Morphological synapomorphies include a trailing, climbing or bushy growth habit, simple petiolate generally three- to five-lobed leaf blades, unisexual (rarely androgynous) inflorescences, triplicate sigmoid anthers, and fleshy often tuberculate or spiny fruits with many compressed whitish seeds. Monophyly of the genus has been disputed in previous studies, but with only limited sampling. Relationships within Cucumis are thus poorly understood. Moreover, the validity of several closely related segregate genera has not been thoroughly tested. In this study, chloroplast (trnS-trnG) and nuclear (ITS) DNA sequences from 40 ingroup and three outgroup taxa were generated and analyzed under parsimony and Bayesian methods. Resulting phylogenies were used to test the monophyly of Cucumis and its sectional circumscriptions, to evaluate whether the related genera represent distinct lineages, and to determine the continental origin of the genus. We recovered six well-supported clades and three subclades, which in some instances represent the first phylogenetically-derived hypotheses of relationships, whereas others either mirror or contradict previous morphologically-based hypotheses of relationships. Morphological, taxonomic and biogeographical implications of these results are discussed. Potential cases of hybridization are also suggested by several well-supported conflicts between the nuclear and chloroplast gene trees.
Log in to add this item to your schedule
1 - Saint Louis University, Department of Biology, 3507 Laclede Avenue, St Louis, Missouri, 63103-2010, USA
2 - University of Uppsala, Department of Systematic Botany, Norbyvagen 18D SE-752 36, Uppsala, Sweden
Presentation Type: Poster:Posters for Sections
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM