Faden, Robert B. , Layton, Daniel J. , Burns, Jean H. , Wurdack, Kenneth .
Non-molecular characters and diversification in African Commelina (Commelinaceae).
With about 170 species the cosmopolitan genus Commelina is the largest in the family. Its center of diversity is tropical Africa, where the 100 native species exhibit the whole range of variation in habit, inflorescence and floral morphology, flower color, capsule dehiscence, adaptations for animal dispersal of seeds, leaf anatomy and basic chromosome number present in the genus as a whole. The genus is most diverse south and east of the lower Guinea-Congolian forest, but pockets of endemism also occur in southern Africa, the Horn of Africa and in West Africa. Some speciation has also occurred within the tropical rainforest, but overall the diversity of forest species is low compared with that in non-forest habitats. The Commelina spathe provides defense for the enclosed buds and developing fruits by serving as a physical barrier as well as a protection against desiccation through the secretion of a mucilaginous liquid by glandular hairs inside. The spathe is very conservative in its structure making the genus very easy to recognize but the species difficult to distinguish. A two-gene phylogeny of 22 Commelina species (Burns et al., in press) showed that fusion of the spathe margins, which would enable the spathe to retain more of the secreted liquid, was a fundamental advancement within the genus. Our working hypothesis is that there are four groups of Commelina species in Africa – none corresponding to any previous classification -- that can be defined by their leaf anatomy, spathe margin fusion, presence or absence of hook-hairs, floral morphology and color, and capsule dehiscence. Each group has a characteristic distribution within Africa. We expect to have more phylogenetic results to test the validity of these groups.
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1 - Smithsonian Institution, Department of Botany MRC 166, National Museum Of Natural History, Po Box 37012, Washington, DC, 20560-0166, USA
2 - 670 Keyser Run Road, Washington, VA, 22747, USA
3 - University of California, Davis, Center for Population Biology, 2320 Storer Hall, One Shields Avenue, Davis, CA, 95616, USA
4 - Smithsonian Institution, Department of Botany, mrc 166, P.O. Box 37012, Washington, DC, 20013-7012, USA
Presentation Type: Oral Paper:Papers for Sections
Location: 555A/Convention Center
Date: Monday, August 2nd, 2010
Time: 11:00 AM