An expanded Pappostipa (Stipeae, Poaceae) includes a lineage of South American species with plumose-like awns

Abstract

Generic delimitation within the tribe Stipeae has been a dynamic process since the late 1980s. In this study, we focus on a morphologically cohesive group of Jarava species with plumose-like awns that previous phylogenetic studies suggested were sister to the genus Pappostipa and only distantly related to Jarava sensu stricto. To test this hypothesis, we broadened species sampling, analysed lemma epidermal patterns, and performed molecular phylogenetic analyses using the nuclear ITS region and three plastid (rpl32-trnL, rps16-trnK, rps16 intron) markers. Phylogenetic results confirmed the close relationship of Jarava species with plumose awns (i.e., the Ptilostipa clade) to species of Pappostipa, forming a wellsupported clade (C subclade). This result is supported by lemma epidermal patterns in the Ptilostipa clade that are similar to the ‘Maize-like’ pattern of the Achnatherum subtype found in Pappostipa. Consequently, we expand Pappostipa to include three species of Jarava (i.e., Pappostipa neaei, comb. nov., P. pogonathera, comb. nov., and P. psylantha, comb. nov.) and we place them in a new section, Pappostipa sect. Ptilostipa, sect. nov. Moreover, we provide new diagnostic features for Pappostipa, including drawings and photographs illustrating floret morphology, lemma epidermal surfaces, species’ habit, and notes on distribution.