Systematics Section / ASPT
Chacon, Juliana , Madriñan, Santiago , Tohme, Joe .
Phylogenetic patterns in the genus Manihot (Euphorbiaceae) inferred from a combined analysis of six DNA regions.
The genus Manihot (Euphorphiaceae) is composed by 98 species distributed from Arizona to Argentina, and the West Indies. They show a disjunct distribution, where none of the North and Central American species are found in South America. There are two centers of diversity, primarily in Brazil, and secondarily in Mexico and Guatemala. Although suprageneric relationships of Manihot are well understood, phylogenetic relationships among species are uncertain. Current studies have emphasized mainly the origin of cassava (Manihot esculenta subsp. esculenta), one of the most important crops in tropical countries. Rogers & Appan proposed the most recent monograph of the genus, using the principles of numerical taxonomy to analyze different morphological characters. Posterior studies based on RFLP data showed high levels of homoplasy in the characters chosen by these authors, reflecting the recent origin of species. In order to establish the molecular phylogeny of Manihot, three plastid regions (accD-psaI spacer, trnL-F spacer, and trnL intron), a nuclear DNA gene (G3pdh) and two ESTs were sequenced. Cnidoscolus spp. were included as outgroup. A Maximum Parsimony analysis was conducted for the combined data set, due to the low variability found in each region independently. The strict consensus tree places the Manihot esculenta subspecies in a basal polytomy, showing the conflict among data sets. This may be a consequence of lateral transfer or hybridization events among species, characteristic of young groups such as Manihot. The rest of the South American species form a grade, and the two Central American species samples form a well-defined clade. This suggests a Cerrado origin for the genus with further diversification in South America, and a single crossing of the Panama land bridge into Central America.
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Laboratorio de Botanica y Sistematica
1 - Universidad de los Andes, Departamento de Ciencias Biologicas, Laboratorio de Botanica y Sistematica, Apartado Aereo 4976, Bogota, DC, 00001, Colombia
2 - International Center for Tropical Agriculture-CIAT, Biotechnology Research Unit, Apartado Aereo 6713, Cali, Valle, 00001, Colombia
Presentation Type: Poster:Posters for Sections
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM