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

Abstract

[EN]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.