Hoch, Peter , Barber, Janet , Diazgranados, Mauricio .
Phylogeny and biogeography of Ludwigia (Onagraceae).
Ludwigia is a diverse widespread 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 biogeographical pattern, with 10 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. The family appears to have originated about 93 Ma, and Ludwigia arose between 93 and 80Ma. No molecular phylogeny is available for Ludwigia, and the considerable age of the clade makes interpretation of the morphology particularly challenging, 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 elucidate the complex biogeographical history of the genus, especially as it relates to the origin of the family. Preliminary data (cpDNA and nDNA sequences from 24 taxa) show good resolution of strong monophyly of the genus and of at least some groups (sect. Oligospermum, and the North American sections), although it appears that the chromosomally complex North American sections Isnardia and Microcarpium may be paraphyletic. Substantial additional sampling is needed, particularly in the South American sections. Recent explosive invasions, particularly by L. hexapetala and relatives 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, P.O. Box 299, St. Louis, MO, 63166-0299, USA
2 - Saint Louis University, Biology, 3507 Laclede Ave., St. Louis, MO, 63103, USA
Presentation Type: Poster:Posters for Topics
Location: Khorassan Ballroom/Chase Park Plaza
Date: Monday, July 11th, 2011
Time: 5:30 PM