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Systematics Section / ASPT

Les, Donald [1], Moody, Michael [1], Jacobs, Surrey [2].

Phylogeny and systematics of Aponogeton (Aponogetonaceae) with an emphasis on Australian species.

Aponogeton (water hawthorne) comprises 45 freshwater monocot species distributed in the Old World tropics. Many species are important aquarium and water garden plants. Van Bruggen’s 1985 monograph provided a taxonomic framework for the genus and included a diagram of hypothetical interspecific relationships which identified the Malagasy A. longiplumulosus as ancestral and indicated poor phylogenetic integrity for most sections. Australian/New Guinea taxa were depicted as monophyletic with exception of A. hexatepalus, an unusual Australian endemic. More recently, several new Australian species have been proposed but details of their relationships have not been determined. We studied phylogenetic relationships among 17 Aponogeton taxa including all nine currently recognized Australian species. Data were analyzed from 25 morphological characters and sequences obtained from cpDNA (trnK5’ intron) and nrDNA (ITS 1-2). Trees were rooted using Juncaginaceae sequences as outgroups. The cpDNA and nrDNA trees were largely congruent and combined analysis indicated that A. hexatepalus is basal followed next by a grade consisting of A. distachyos (Africa) and A. robinsonii (Indo-China). Malagasy species occur within a monophyletic clade adjacent to a major clade consisting of Indian, southeast Asian and Australian species. Australian species (less A. hexatepalus) are strongly supported as a monophyletic subclade. Several Australian species (A. bullosus, A. lancesmithii, A. proliferus) are distinct morphologically but lack molecular divergence, possibly indicating their recent radiative speciation. Morphological data provided little resolution but supported several molecular results (e.g., relationship of A. euryspermus and A. vanbruggenii; A. proliferus and A. bullosus). Overall, molecular data supported Van Bruggen’s sectional limits in Aponogeton much better than relationships based on his morphological trends. We also found paralogous sequences probably resulting from polyploidy and evidence indicating hybridization involving A. madagascariensis, A. vanbruggenii and A. queenslandicus.

1 - University of Connecticut, Ecology & Evolutionary Biology, 75 North Eagleville Rd., Storrs, Connecticut, 06269-3043, USA
2 - Royal Botanical Gardens, Sydney, New South Wales, 2000, Australia

molecular systematics
aquatic plants

Presentation Type: Paper
Session: 2-4
Location: Cottonwood A (Snowbird Center)
Date: Monday, August 2nd, 2004
Time: 8:45 AM
Abstract ID:107

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