Triplett, Jimmy K. , Zhong, Jinshun , Simpson, Aileen , Kellogg, Elizabeth .
Phylogenetic relationships and allopolyploid origins within Panicum sensu stricto (Poaceae: Panicoideae), as inferred from multiple nuclear and plastid loci.
The genus Panicum sensu stricto includes approximately 100 species in five sections defined on the basis of morphology. Sections Panicum, Dichotomiflora, and Virgata are distributed worldwide, while Rudgeana occurs from South to Central America and Urvilleana is restricted to North America. Previous investigations using plastid data clearly established the monophyly of Panicum s.s.; however, little is certain about species-level relationships within or among the five sections. The current study is aimed at understanding relationships in Panicum with an emphasis on the potential biofuel species, switchgrass (P. virgatum), and its relatives in sections Virgata and Urvilleana. We complemented plastid data with cloned sequences from low-copy nuclear genes encoding alcohol dehydrogenase (adh1), knotted1 (kn1), two endo-1,4-β glucanases, and a putative poly-A binding protein in order to explore the evolutionary history of Panicum and the origin of allopolyploid lineages. Nuclear gene tree topologies were highly concordant and revealed divergent homoeologous sequences within each section of Panicum. Phylogenetic analyses indicate that an ancestral hybridization event occurred prior to the divergence of Virgata and Urvilleana, followed by speciation at the tetraploid level. There is little genetic differentiation between P. virgatum and other species in these sections, raising the possibility that the gene pool of switchgrass includes other species. Moreover, several species appear to be polyphyletic, including P. virgatum, P. amarum, and P. chloroleucum. Previously unplaced species P. olyroides and P. mystasipum are nested within the monophyletic section Rudgeana, and appear to be among the closest extant relatives of one of the two genomes in Virgata and Urvilleana. The emergent phylogeny will be discussed in the context of taxonomy, genetics, and biogeography.
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1 - University of Missouri-St. Louis, Department of Biology, One University Boulevard, St. Louis, Missouri, 63121, USA
low copy nuclear markers
Presentation Type: Oral Paper:Papers for BSA Sections
Location: Cottonwood D/Snowbird Center
Date: Wednesday, July 29th, 2009
Time: 5:00 PM