Molecules and morphology in South American Stipeae (Poaceae)

BARKWORTH, M.E.; ARRIAGA, M.O.; SMITH, J.F.; JACOBS, S.W.L.; VALDES-REYNA, J.; BUSHMAN, S

SYSTEMATIC BOTANY

USDA-ARS-SHRS

Lugar: Miami, Florida, USA; Año: 2008 vol. 33 p. 719 - 731

0363-6445

We conducted cladistic analyses of molecular data (ITS, trnH-psbA, trnC-trnL, and trnK-rps16) from 74 species of stipoid grasses. Of these species, 31 are native to South America, 7 are native to Mexico and/or the southern United States, 54 to the northern North America, 1 to southern and northern North America, 14 to Eurasia or the Mediterranean region, and 6 to Australia. The outgroup was Glyceria declinata, a member of the Meliceae. 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 Aikake information 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, is needed to develop a robust phylogeny of the South American members of the Stipeae.