Insights to the taxonomy and phylogeny of the genus Ptilagrostis worldwide (Poaceae, Stipeae) with a key to species identification, checklist and outlines for further studies.

Abstract

Ptilagrostis (false needlegrass) is a genus of high-mountain grasses distributed in Central and North-East Asia, as well as in North America. The phylogenetic position of the genus Ptilagrostis within the Stipeae is well defined based on micromorphological patterns of lemma epidermis and moleculs. However, there is a lack of a comprehensive taxonomic revision of the genus in its entire distribution range. In this study, we performed comprehensive analyses using integrative taxonomic methods, aiming at both micromorphological and macromorphological analyses, and molecular analyses based on SNPs obtained from DArT genome-wide sequencing, in which we considered all taxa representing the genus in order to establish phylogenetic relationships between its members. We analysed all species possessing the characteristic 'Ptilagrostis pattern' of the lemma epidermis, with a particular reference to species possessing the terminal segment of the awn (seta) covered by short (up to 1 mm long) hairs that, until now, were treated as representatives of the genus Achnatherum. Following with the result of our molecular, morphological and anatomical analyses, the genus Ptilagrostis is represented by 15 species, one subspecies and five varieties organised in three well supported phylogenetic clades corresponding to the three sections: Ptilagrostis, Barkworthia and Chenella. In this paper, we provide an original key to identifying false needlegrass species, together with a checklist containing the intrageneric species-organisation. In addition, for each species, we present the data regarding nomenclatural types, morphological description, and information on the geographical distribution, habitat preferences and altitudinal ranges. We proposed two new varieties within the genus Ptilagrostis, P.glabrifoliavar.himalayensis and P.concinnavar.xizangensis, and the new section Chenella comprising three species with awns scabrous or covered by very short hairs up to 0.3 mm long. Additionally, we transfer Stipachingii to Ptilagrostischingii, Achnatherumchingiivar.laxum to P.chingiivar.laxum, and Ptilagrostisconcinnasubsp.schischkinii to P.junatoviivar.schischkinii. Lectotypification was made for three taxa, Stipamongholicavar.minutiflora, P.czekanowskii, and P.tibetica.