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Abstract Detail


Systematics Section / ASPT

Tippery, Nicholas P. [1], Les, Donald H. [1], Padgett, Donald [2], Jacobs, Surrey [3].

Clades and grades: an evaluation of generic circumscriptions in Menyanthaceae Dumort. (Asterales).

MENYANTHACEAE consist of five genera of aquatic and wetland plants distributed nearly worldwide. Recent angiosperm phylogeny investigations resolve the family decidedly within Asterales in a clade with Asteraceae, Calyceraceae and Goodeniaceae. However, relationships within the family have remained ambiguous. Although three genera (Liparophyllum, Menyanthes, Nephrophyllidium) are monotypic and well-defined, species often are difficult to assign to either of the two largest genera (Nymphoides, Villarsia) as presently circumscribed. We have conducted a phylogenetic analysis of the five genera recognized traditionally in the family using a combination of morphological and molecular data to test their monophyly. Several loci (rbcL, matK, trnK 3’,5’introns, nrITS) yield congruent topologies (as indicated by partition-homogeneity test) and produce a fairly well-resolved and well-supported phylogeny when combined. Parsimony/Bayesian analyses indicate that Menyanthes and Nephrophyllidium (northern hemisphere) occur within a well-supported clade that is basal to the remaining genera. With exception of the morphologically anomalous Nymphoides exigua (e.g., reduced leaves and inflorescences), the remainder of Nymphoides species resolve within a strongly-supported clade. Villarsia is polyphyletic with species distributed among three different groups: 1) an Australian clade of emergents, 2) a grade including the Australian Nymphoides exigua and Liparophyllum gunnii and 3) an isolated clade consisting only of the South African Villarsia capensis. Precise relationships within the Villarsia/Nymphoides/Liparophyllum grade are difficult to determine and will require further taxon sampling for elucidation. The isolated placement of Villarsia capensis (the type of the genus) necessitates a reconsideration of the classification. A clade of Nymphoides species having floating leaves and modified inflorescence (including the dioecious Nymphoides cordata) is derived within the genus. Phylogenetic analyses indicate a transition between emergent wetland plants and floating-leaved aquatics with morphologically intermediate taxa whose phylogenetic relationships remain difficult to resolve using morphological or molecular data.


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1 - University of Connecticut, Ecology & Evolutionary Biology, 75 North Eagleville Road, U-3043, Storrs, Connecticut, 062693043, USA
2 - Bridgewater State College, Department of Biological Sciences, Bridgewater, Massachusetts, 02325, USA
3 - Royal Botanic Gardens, Mrs Macquaries Road, Sydney, New South Wales, 2000, Australia

Keywords:
Asterales
Phylogenetics
Taxonomy
Australian flora
Dioecy
heterostyly.

Presentation Type: Oral Paper:Papers for Sections
Session: 74-3
Location: 120/Ayres
Date: Wednesday, August 2nd, 2006
Time: 1:30 PM
Abstract ID:577


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