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Abstract Detail

Systematics Section / ASPT

Mort, Mark E. [1], Randle, Christopher P. [1], Burgoyne, Priscilla M. [2], Smith, Gideon F. [2], Tolken, Helmut [3], Hopper, Steven [4], van Jaarsveld, Ernst [5].

Molecular phylogenetics of Crassula (Crassulaceae) inferred from nuclear and plastid DNA sequences: patterns of evolution and dispersal.

THE genus Crassula (Crassulaceae) includes approximately 150 species, and exhibits broad diversity in habit, base chromosome number and floral morphology. Broad phylogenetic studies of Crassulaceae strongly support the monophyly of the genus and place it as sister to the remainder of the family. Within the genus, two subgenera and 20 sections have been recognized. Species of subgenus Crassula are all endemic to southern Africa, perennial, and are highly succulent and often display a range of woodiness. The subgenus comprises species that display many growth forms, ranging from columnar, succulent herbs to arborescent forms. On the other hand, subgenus Disporocarpa includes both perennial and annual species; the annuals often inhabit aquatic and semi-aquatic habitats. In contrast to subgenus Crassula members of of subgenus Disporocarpa are geographically widespread and occur throughout Africa, as well as parts of Asia, Europe, Oceania and North and South America. Most species naturally occurring outside of southern Africa are aquatic (to semi-aquatic) annuals. Preliminary phylogenetic analysis indicates that there have been multiple origins of the annual habit within Disporocarpa, itself a basal grade; there is strong support for the monophyly of subgenus Crassula. In this study, chloroplast and nuclear DNA sequences were obtained from southern African and Australian species of Crassula to investigate 1) biogeography of subgenus Disporocarpa, 2) variation in the rate of nucleotide substitution between perennial and annual lineages.

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1 - University of Kansas, Department of Ecology & Evolutionary Biology, Natural History Museum and Biodiversity Research Center, 1200 Sunnyside Avenue, Lawrence, Kansas, 66045-7534, USA
2 - National Herbarium (Pretoria), Private Bag X101, Pretoria, 0001, Republic of South Africa
3 - State Herbarium, Department for Environment and Heritage, Plant Biodiversity Centre, P.O.Box 2732, Kent Town, SA 5071, Australia
4 - The University of Western Australia, Faculty of Natural and Agricultural Sciences, School of Plant Biology - MO82, 35 Stirling Highway, Crawley, , Australia
5 - Kirstenbosch National Botanical Garden, Rhodes Avenue, Newlands, Cape Town, , South Africa

South Africa

Presentation Type: Oral Paper:Papers for Sections
Session: 19-2
Location: 106/Ayres
Date: Monday, July 31st, 2006
Time: 1:15 PM
Abstract ID:554

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