Colloquium: The flora of Madagascar: research needs and research progress
Skema, Cynthia .
Big genera of Madagascar: Tackling the systematics of Dombeya (Pentapetaceae or Malvaceae s.l.).
Dombeya (Pentapetaceae or Malvaceae s.l.) is a prime example of one of the last major hurdles left in the completion of the flora of Madagascar: undercollected, highly speciose genera. Constituting almost 2% of the Malagasy flora, this genus demonstrates the megadiversity on the island with roughly 180 of its 210 species occurring there. Evidence for the lack of collections of Dombeya from Madagascar can be seen in its last treatment done in 1959 by ArĂ¨nes wherein over 40% of the species were described from a type specimen only. Despite its ubiquity in many habits throughout the island, Dombeya remains taxonomically neglected in Madagascar and no phylogeny has ever been hypothesized for the genus. A phylogenetic study of chloroplast markers (e.g. trnDpsbM, trnCycf6, psbMycf6) and nuclear regions (e.g. cesA) is ongoing. Sampling includes taxa from over 200 newly collected specimens of Dombeya and a wide range of outgroups within Pentapetaceae from Madagascar and Asia. Molecular data within Dombeya show a surprising lack of variation given the range in morphology and number of taxa sampled. Preliminary parsimony analyses suggest that Dombeya is not monophyletic, with Paramelhania and Trochetiopsis nested within it, but with only low bootstrap support. Past treatments have relied on morphological characters of apparently little evolutionary relevance, such as persistence of floral parts, epicalyx fusion and cotyledon attributes. To begin construction of a more natural classification of Dombeya and its relatives, a concurrent search for new morphological characters to define the monophyletic groups within this new phylogenetic framework is also underway.
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1 - Cornell University, L.H. Bailey Hortorium, Department of Plant Biology, 412 Mann Library, Ithaca, NY, 14853, USA
Presentation Type: Symposium or Colloquium Presentation
Location: Blair B/Gage
Date: Tuesday, July 29th, 2008
Time: 9:30 AM