Romaschenko, Konstantin , Peterson, Paul M. , Soreng, Robert J. , Garcia-Jacas, Nuria , Susanna, Alfonso .
A phylogeny of Stipeae (Poaceae: Pooideae) based on plastid and nuclear DNA sequence data.
The Stipeae tribe is a group of 400−600 grass species of worldwide distribution that are currently placed in 21 genera. The “needlegrasses” are characterized by having single-flowered spikelets and stout, terminally-awned (awn composed of more than one vein) lemmas. We conducted a molecular phylogenetic study of the Stipeae (21 genera) using 140 species (17 additional species were used as outgroups) based on nine plastid DNA sequences (trnK-5’matK, matK, trnHGUG-psbA, trnL5’-trnF, ndhF, rps16-trnK, rps16-intron, rps3, and rpl32-trnLUAG) and a single nuclear ITS DNA sequence. Our parsimony analysis of DNA sequences supports: the monophyly of the Stipeae including Macrochloa as sister to all other Stipeae; the recognition of Lorenzochloa (L. erectifolia) since it does not align with Ortachne but with some species of Aciachne and Anatherostipa; Ptilagrostis s.l. as occurring in four separate clades; and Oryzopsis as a monotypic genus (O. asperifolia). Achnatherum and Piptatherum as currently circumscribed are polyphyletic and we provide good support to split the former into five groups: Achantherum, “Neotrinia”, and a Timouria s.l. clade in the Old World, Eriocoma and “Pseudoeriocoma” in the New World; and the latter into four groups (Achnatherum p.p. typica, Piptatherum, “Miliacea” in the Old World, and a North American “Piptatheropsis” clade). Achnatherum s.s., Austrostipa, Hesperostipa, Jarava s.s., Ortachne s.s., Pappostipa, Piptatherum s.s., Piptochaetium, Ptilagrostis s.s., Stipa s.s., and Trikeraia are all well supported as monophyletic genera. Stipa capensis and S. parviflora both of African origins are apparently misplaced and are not closely related to other species of Stipa s.s. but are allied to achnatheroids. Based on molecular evolution of plastid sequences and lemma epidermal pattern we present a stepwise model for the evolution of the Stipeae with two initial and deep bifurcations followed by two further bifurcations that are geographically consistent with parallel New and Old World diversifications.
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1 - Smithsonian, Department of Botany, National Museum of Natural History, P.O. Box 37012, Washington, DC, 20013, USA
2 - Botanical Institution of Barcelona, Botany, p/g Migdia S/N, Barcelona, Cataluna, 08038, Spain
Presentation Type: Oral Paper:Papers for BSA Sections
Location: Cottonwood D/Snowbird Center
Date: Wednesday, July 29th, 2009
Time: 3:45 PM