Pennisetum (80–140 species) and Cenchrus (16–22 species) are closely related genera of Paniceae, both distributed in tropical and sub-tropical regions. The distinction between Pennisetum and Cenchrus is not clearly defined, and currently no comprehensive taxonomic treatment is available for either genus. Chloroplast DNA sequence data (rpl16, trnL-F region) were analyzed to test their monophyly, species relationships, and infrageneric classifications. Phylogenetic analyses of individual genomic regions, and a combined dataset, including indel-coded information, were performed under parsimony and Bayesian inference. Selected geographical, chromosomal and morphological characters were mapped onto the phylogeny to investigate evolutionary trends. Our results support a monophyletic bristle clade and the close relationship between Pennisetum and Cenchrus. Excluding Pennisetum lanatum, Pennisetum is paraphyletic because Cenchrus is nested within it. Sections Pennisetum and Gymnotrix are polyphyletic. Our molecular phylogenetic results show a close relationship among the domesticated species P. glaucum, P. purpureum, P. squamulatum, P. nervosum, and P. sieberianum, suggesting the potential use of these species in crop improvement. The Pennisetum-Cenchrus clade shows an independent reduction (x = 5, 7, 8) or duplication (x = 17) of the basic chromosome number from the ancestral x = 9. American Pennisetum and Cenchrus species appear to have originated from Old World species more than once. A core group of American species of Cenchrus with a basic chromosome number of x = 17 and retrorsely barbed bristles could be restricted to Cenchrus s. str.
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Document Type: Research Article
Instituto de Botánica Darwinion, Labardén 200, C.C. 22, B1642HYD, San Isidro, Argentina;, Email: [email protected]
Instituto de Botánica Darwinion, Labardén 200, C.C. 22, B1642HYD, San Isidro, Argentina
University of Missouri–St. Louis, Department of Biology, One University Boulevard, St. Louis, Missouri 63121. U.S.A.
Publication date: 01 May 2009
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