Systematics Section / ASPT
Peterson, Paul M. , Saarela, Jeffery M. .
A phylogeny of Calamagrostis (Poaceae: Agrostidinae) and related genera based on plastid and nuclear DNA sequence data.
In the New World (western hemisphere) Calamagrostis contains approximately 133 species, with the greatest diversity occurring in South America where the genus has traditionally been referred to as Deyeuxia. Calamagrostis is characterized as having single-flowered spikelets, one to three-veined glumes as long or exceeding the floret in length, non-keeled lemmas that are membranous or cartilaginous, usually with a single dorsally attached awn (rarely awnless), a callus with a crown of hairs, and a base chromosome number of x = 7. Many of these same morphological features are shared by species of Agrostis (@220 spp.), Chascolytrum (6 spp.), Hierochloe (30 spp.), Peyritschia (7 spp.), Polypogon (18 spp.), Torreyochloa (4 spp.), and Trisetum (90 spp.). In Calamagrostis, all species analyzed to date are polyploids, and prior evidence indicates that its evolution likely involved inter and intraspecific hybridization events that obscure species boundaries. We have begun a collaborative project to investigate the phylogenetic relationships among all species of Calamagrostis in the New World using plastid and nuclear DNA sequence data. A preliminary phylogenetic analysis based on trnL-F sequence data indicates that there are apparently two distinct lineages within Calamagrostis, and that the genus is paraphyletic; within these two clades, species of Agrostis, Chascolytrum, Hierochloe, Peyritschia, Polypogon, and Trisetum are embedded. All species of Calamagrostis, Peyritschia, and Trisetum within one of the clades are from Mexico, whereas all species of Calamagrostis in another clade have North American or European origins. This deep split within Calamagrostis may indicate that there were two major areas of diversification, one that occurred along the Andean Cordillera in South America and the other that corresponds to a north temperate or circumboreal dispersal route between Europe and North America. We hope to answer these questions with a more robust data set that includes more sequence data and more species.
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1 - Smithsonian, Botany, National Museum of Natural History, Washington, DC, 20013-7012, USA
2 - Canadian Museum of Nature, Research Division, Po Box 3443, Station D, Ottawa, Ontario, K1P 6P4, Canada
Presentation Type: Oral Paper:Papers for Sections
Location: Continental A/Hilton
Date: Tuesday, July 10th, 2007
Time: 8:45 AM