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Abstract Detail

Systematics Section / ASPT

Csizmadi, Jessie [1], Snow, Neil [1], Wojciechowski, Martin F. [2], Salywon, Andrew [3], Beresford, Guy [1].

Testing generic boundaries of Rhodomyrtus (Myrtaceae) using ITS sequence data and morphology.

RHODOMYRTUS (Myrtaceae) consists of approximately 20 species ranging from southern Asia and the Philippines to Australia, New Caledonia and the Solomon Islands. Some taxonomists have doubted the monophyly of Rhodomyrtus, which has been recognized based on some combination of the following characters: 5-merous flowers, acrodromous leaf venation, axile placentation, and fleshy fruits. However, brochidodromous venation occurs in about half the species, although no other known morphological trait is also shared by that group of species. We tested the null hypothesis that Rhodomyrtus is monophyletic using ITS data by sequencing nearly all species of the genus and one to several representatives of possibly related Australasian genera (Archirhodomyrtus, Octamyrtus, Pilidiostigma, Gen. Nov. from New Caledonia, Decaspermum, Rhodamnia, and Myrtastrum). Results from parsimony and maximum likelihood consistently rejected the null hypothesis that Rhodomyrtus is monophyletic. In all trees the species of Rhodomyrtus segregate into two Clades (A, B) that are separated by up to three genera. Clades A and B each contain brochidodromous and acrodromous species and other taxa not in Rhodomyrtus. For example, each Clade has one species of Octamyrtus, whereas Clade A also has one species of Gen. Nov. and one of Archirhodomyrtus. A morphological-based phylogeny of Rhodomyrtus was not inferred given insufficient data for that genus and some of the related genera. However, we used MacClade to modify a likelihood-based constraint tree to examine character evolution among some traits considered taxonomically useful a priori to see what effect the movement of branches had on tree length. Forcing all brochidodromous species of Rhodomyrtus into one clade based on the minimum number of drag-and-drop events led to significant decrease in tree length based on the morphological data available (23 characters). We present briefly a newly recognized species of Rhodomyrtus from Papua New Guinea.

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1 - University of Northern Colorado, School of Biological Sciences, Greeley, Colorado, 80639, USA
2 - Arizona State University, School of Life Sciences, P.O. Box 874501, Tempe, Arizona, 85287-4501, USA
3 - USDA, Agricultural Research Service, U.S. Arid-Lands Reseach Center, 21881 N. Cardon Lane, Maricopa, Arizona, 85239, USA

ITS sequencing

Presentation Type: Oral Paper:Papers for Sections
Session: 30-10
Location: 134/Performing Arts Center
Date: Tuesday, August 1st, 2006
Time: 10:45 AM
Abstract ID:492

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