Phylogenetics of Piptatherum s.l. (Poaceae: Stipeae): Evidence for a new genus, Piptatheropsis, and resurrection of Patis

Abstract

Historically, there has been taxonomic confusion among agrostologists regarding the short–spikeleted Stipeae. We refer to these as the Oryzopsis/Piptatherum complex which consists of short–spikeleted species with coriaceous to cartilaginous and often caducous–awned lemmas, and florets with a blunt callus. We conducted a phylogenetic analysis of 53 species that have been associated with this complex using four plastid regions (ndhF, rpl32–trnL, rps16–trnK, rps16 intron) in combination with lemma micromorphology to infer evolutionary relationships. Piptatherum as currently circumscribed is polyphyletic and is found in five strongly supported clades in our maximum likelihood tree. Based on our phylogenetic and morphological evidence we recognize a Eurasian Piptatherum s.str., propose a new genus, Piptatheropsis, to include five North American species, and resurrect the genus Patis to include three species, two from Eurasia and one from North America. We provide morphological descriptions of Patis, Piptatherum, and Piptatheropsis, and provide keys to the genera and species of the Oryzopsis/Piptatherum complex. The following new combinations are made: Patis obtusa, Patis racemosa, Piptatheropsis canadensis, Piptatheropsis exigua, Piptatheropsis micrantha, Piptatheropsis pungens, Piptatheropsis shoshoneana, Piptatherum brachycladum, and Piptatherum kopetdagense.

A multi-locus analysis of phylogenetic relationships within grass subfamily Pooideae (Poaceae) inferred from sequences of nuclear single copy gene regions compared with plastid DNA

“…The position of Ampelodesmos in the Stipeae and the monophyly of this group (Fig. 2) is supported by several previous molecular phylogenetic studies (Bouchenak-Khelladi et al, 2008;Soreng, 1993, 2007;Döring et al, 2007;Duvall et al, 2007;GPWG II, 2012;Hamasha et al, 2011;Romaschenko et al, 2011Romaschenko et al, , 2012Romaschenko et al, , 2014Schneider et al, 2009Schneider et al, , 2011Soreng and Davis, 1998). The genus is sometimes placed in the monotypic subtribe Ampelodesminae (Schneider et al, 2009;Soreng et al, 2003Soreng et al, , 2014.…”

Flowering Plants. Monocots

“…This species is unrelated to Achnatherum s.s. but is strongly supported as sister to Psammochloa villosa (Hamasha et al 2012;Romaschenko et al 2011Romaschenko et al , 2012.…”

“…Generic limits within this tribe are problematical and in a state of flux (Barkworth et al 2008;Romaschenko et al 2008Romaschenko et al , 2010Romaschenko et al , 2011Romaschenko et al , 2012. Traditional taxonomy separated plants with short roundish spikelets from those with narrow elongate spikelets, but this distinction is wholly artificial and does not indicate relationship .…”

“…Traditional taxonomy separated plants with short roundish spikelets from those with narrow elongate spikelets, but this distinction is wholly artificial and does not indicate relationship . The phylogenetic analyses of Romaschenko et al (2010Romaschenko et al ( , 2011Romaschenko et al ( , 2012 place Macrochloa sister to all other members of the tribe, which is then divided into four clades. Clade I includes an Old World subclade (Stipa s.s., Ampelodesmos, Psammochloa, Oryzopsis s.s., Trikeraia, Orthoraphium, and Ptilagrostis, plus the New World Oryzopsis s.s.), and a New World subclade (Aciachne, Anatherostipa, Hesperostipa, Lorenzochloa, Ortachne, Piptatheropsis, Piptochaetium, and Pappostipa).…”

“…Although Romaschenko et al (2011Romaschenko et al ( , 2012 place "P." kingii sister to Piptatheropsis, support for this is weak. There is little morphological similarity between the two.…”