Systematics Section / ASPT
Hoch, Peter C. , Barber, Janet C. .
Phylogenetics of Ludwigia, an ancient plant lineage.
Ludwigia is a diverse pantropical genus of 82 species currently divided into 23 sections. Fourteen of the sections are monotypic, and only three have more than five species. The genus exhibits a complex biogeographic pattern, withÂ nine sections endemic to or centered in South/Central America, three in North America, four in Africa, three in Asia, two in the Paleotropics, and two are cosmopolitan. Polyploidy is widespread, with gametic chromosome numbers from n = 8 to n = 64. Strong molecular and morphological data place Ludwigia as sister to the rest of the Onagraceae, so understanding its phylogeny is crucial to understanding the family. No molecular phylogeny is available, and morphological data are hard to interpret, so we have undertaken a comprehensive phylogenetic analysis of Ludwigia in order to assess the validity of this highly fragmented classification, test relationships among sections and species, and determine the biogeographical history of the genus. Preliminary data (ITS sequence from 24 taxa) show good resolution of strong monophyly of the genus and of at least some sections (Oligospermum, Ludwigia) but apparent paraphyly of the chromosomally complex North American sections Isnardia and Microcarpium. Substantial additional sampling is needed, particularly in the South American sections. Recent explosive invasions in wUSA, Australia, and southern Europe highlight the need for a comprehensive modern revision and phylogeny in order to identify and possibly control these invasives.
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1 - Missouri Botanical Garden, Po Box 299, St Louis, Missouri, 63166-0299, USA
2 - Saint Louis University, Department of Biology, 3507 Laclede Avenue, St Louis, Missouri, 63103-2010, USA
Presentation Type: Oral Paper:Papers for Sections
Location: Stevens 3/Hilton
Date: Wednesday, July 11th, 2007
Time: 2:00 PM