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Abstract Detail

Systematics Section / ASPT

Naczi, Robert F. C. [1], Knapp, Wesley [2].

Circumscription of Rhynchospora section Plumosae (Cyperaceae), based on Morphologic Data.

As a first step toward reconstructing the phylogeny and revising the taxonomy of Rhynchospora section Plumosae, we evaluated the limits of this group. Rhynchospora section Plumosae contains 56 taxa occurring in Central America, the West Indies, the southeastern U.S.A, and possibly northern South America. The current circumscription is for plants having transversely rugulose achene bodies subtended by plumose bristles. Problems with this circumscription include 1) the possibility that the character states currently used to define the section could be plesiomorphic, and 2) the controversial placement of the morphologically and geographically divergent R. diodon. The goals of this project are to test the monophyly of the section and to identify synapomorphies that could diagnose the group. Macromorphology, micromorphology, and anatomy yielded a suite of characters useful for this investigation. Transversely rugulose achene bodies may be apomorphic in Rhynchospora, but this character state is not limited to section Plumosae. The following appear to be synapomorphies that diagnose section Plumosae as a monophyletic group: 1) achene bristles plumose, with trichomes that are twisted when dry, 2) achene bodies covered with epicuticular wax, 3) distal portions of achene bodies sparsely denticulate, and 4) achene bodies suborbicular in cross-section (reversed to elliptical in R. breviseta and R. plumosa). With this diagnosis, the membership of the section is R. breviseta, R. intermedia, R. megaplumosa, R. oligantha, and R. plumosa, though the taxonomy of some of these taxa remains problematic. Rhynchospora diodon does not appear to be a member of section Plumosae because this species lacks all the synapomorphies of the section. As well, the plumose bristles do not appear to be homologous in the two groups. Another important outcome of this project is the identification of micromorphology and anatomy as valuable sources of data for phylogenetic inference in Rhynchospora.

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1 - Delaware State University, Claude E. Phillips Herbarium, Department Agriculture & Natural Resources, 1200 N Dupont Highway, Dover, Delaware, 19901-2277, USA
2 - Delaware State University, Claude E. Phillips Herbarium, Dover, DE, 19901

sectional circumscription.

Presentation Type: Oral Paper:Papers for Sections
Session: CP16
Location: Stevens 3/Hilton
Date: Monday, July 9th, 2007
Time: 4:30 PM
Number: CP16013
Abstract ID:1870

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