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United States Department of Agriculture

Agricultural Research Service

Title: Molecules and Morphology in South American Stipeae (Poaceae)

Authors
item Barkworth, Mary - UTAH STATE UNIVERSITY
item Arriaga, Mirta - HERBARIO
item Smith, James - BOISE STATE UNIVERSITY
item Jacobs, Surrey - NATIONAL HERBARIUM
item Reyna, Jesus - UNIVERSIDAD AUTONOMA
item Bushman, Shaun

Submitted to: Systematic Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 2, 2008
Publication Date: October 1, 2008
Citation: Barkworth, M.E., Arriaga, M.O., Smith, J.F., Jacobs, S.W., Reyna, J.V., Bushman, B.S. 2008. Molecules and Morphology in South American Stipeae (Poaceae). Systematic Botany 33:719-731.

Interpretive Summary: We conducted phylogenetic analyses of molecular data (ITS, trnH-psbA, trnC-trnL, and trnK-rps16) for 73 species of stipoid grasses. Of these species, 30 are native to South America, eight are native to Mexico and/or the southern United States, 14 to northern North America, 14 to Eurasia and/or the Mediterranean region, and seven to Australia. The outgroup was Glyceria declinata, a member of the Meliceae, a tribe that is in the same clade as, and possibly sister to, the Stipeae (GWPG 2001; Salamin et al. 2002). The purpose of the study was to evaluate alternative generic treatments of the South American Stipeae, all of which are based on morphological and anatomical information. Questions of particular interest were the merits of recognizing Amelichloa and the inclusion of Stipa subgg. Pappostipa and Ptilostipa in Jarava. Trees obtained from separate analyses of the ITS and cpDNA data were poorly resolved. The majority rule tree obtained from the combined data support the monophyly of Austrostipa, Hesperostipa, Piptochaetium, Stipa subg. Pappostipa, Nassella + Amelichloa, Aciachne + Anatherostipa, and Hesperostipa+ Piptochaetium + Aciachne + Anatherostipa. Duplicate runs with altered taxon order and with models selected using the different criteria differed only slightly in posterior probability values. The Hesperostipa+ Piptochaetium + Aciachne + Anatherostipa clade is not supported with models selected using the Aikake information criteria for both the ITS and cpDNA data. None of the trees support inclusion of Stipa subg. Pappostipa in Jarava. For subg. Ptilostipa, we obtained no ITS data and cpDNA data for only one species. The cpDNA data placed the species in a clade with two Nassella species. Increased taxon sampling and examination of more genes, particularly nuclear genes, are needed to develop a robust phylogeny of the South American members of the Stipeae.

Technical Abstract: We conducted phylogenetic analyses of molecular data (ITS, trnH-psbA, trnC-trnL, and trnK-rps16) for 73 species of stipoid grasses. Of these species, 30 are native to South America, eight are native to Mexico and/or the southern United States, 14 to northern North America, 14 to Eurasia and/or the Mediterranean region, and seven to Australia. The outgroup was Glyceria declinata, a member of the Meliceae, a tribe that is in the same clade as, and possibly sister to, the Stipeae (GWPG 2001; Salamin et al. 2002). The purpose of the study was to evaluate alternative generic treatments of the South American Stipeae, all of which are based on morphological and anatomical information. Questions of particular interest were the merits of recognizing Amelichloa and the inclusion of Stipa subgg. Pappostipa and Ptilostipa in Jarava. Trees obtained from separate analyses of the ITS and cpDNA data were poorly resolved. The majority rule tree obtained from the combined data supported the monophyly of Austrostipa, Hesperostipa, Piptochaetium, Stipa subg. Pappostipa, Nassella + Amelichloa, Aciachne + Anatherostipa, and Hesperostipa+ Piptochaetium + Aciachne + Anatherostipa. Duplicate runs with altered taxon order and with models selected using the different criteria differed only slightly in posterior probability values. The Hesperostipa+ Piptochaetium + Aciachne + Anatherostipa clade is not supported with models selected using the Aikake information criteria for both the ITS and cpDNA data. None of the trees support inclusion of Stipa subg. Pappostipa in Jarava. For subg. Ptilostipa, we obtained no ITS data and cpDNA data for only one species. The cpDNA data placed the species in a clade with two Nassella species. Increased taxon sampling and examination of more genes, particulary nuclear genes, are needed to develop a robust phylogeny of the South American members of the Stipeae.

Last Modified: 8/29/2014
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