A molecular phylogenetic study of temperate grasses in Poeae chloroplast group 1 (Poaceae: Pooideae: Poeae) based on nuclear ribosomal and plastid DNA sequence data

<div><b>Abstract:</b><br></div>We conducted phylogenetic analyses of >2500 new DNA sequences from nuclear ribosomal (ITS and ETS) and five plastid regions to clarify relationships within and among genera and subtribes that are part of the grass tribe Poeae chloroplast group 1 and allies. A large clade comprises the subtribes Agrostidinae and Calothecinae, neither of which is monophyletic. The type species of Deyeuxia is allied with species of Calamagrostis s.s., thus Deyeuxia is a synonym of Calamagrostis, and relationships among species of Calamagrostis s.str. and related genera are mostly poorly resolved. Agrostis and Polypogon are distinct from Calamagrostis s.s. but are not reciprocally monophyletic. Species of Agrostis and Polypogon are intermixed in a strongly supported clade in plastid trees, including Lachnagrostis, and there is incongruence among data partitions in a subset of species. Ammophila and Calamagrostis s.str. are not distinguished as separate genera, and Calamagrostis coarctata, Dichelachne, Echinopogon and Relchela are closely related. Taxa of Sesleriinae are allied with Aveninae s.s. (Arrhenatherum, Avena, Helictotrichon, Tricholemma) in nuclear ribosomal trees, and with taxa of chloroplast group 2 in plastid trees. Koeleriinae is strongly supported and includes two major subclades: clade A comprises Avellinia, Gaudinia, Graphephorum and Trisetum sect. Trisetum p.p. (nuclear trees), Koeleria, Rostraria, Trisetaria, Trisetum sect. Trisetum p.p. and Trisetum sect. Trisetaera, and Koeleriinae clade B comprises Calamagrostis/Deyeuxia p.p., Graphephorum and Trisetum sect. Trisetum p.p. (plastid trees), Peyritschia, Leptophyllochloa, Sphenopholis, Trisetopsis and Trisetum sect. Deschampsioides. Within each clade most aspects of relationship are unresolved, and conflict between data partitions is identified. Affinities of Lagurus ovatus with respect to Aveninae s.s. and Koeleriinae are incongruent in nuclear ribosomal and plastid trees. All but one of the eight sampled species of Deyeuxia sect. Stylagrostis are part of the Deschampsia lineage, and these are transferred to Deschampsia. Substantial changes to the current classification will be needed to produce generic circumscriptions consistent with phylogenetic evidence.<div><br></div><div><i>Presentation delivered at XIX International Botanical Congress, Shenzhen, China, 23–29 July 2017, in a symposium entitled "Poaceae: systematics and phylogeny of major lineages".</i> </div><div><i><br></i></div><div><b>Related publication:</b></div><div>Saarela JM, Bull RD, Paradis MJ, Ebata SN, Peterson PM, Soreng RJ, Paszko B, . (in press) Molecular phylogenetics of cool-season grasses in the subtribes Agrostidinae, Anthoxanthinae, Aveninae, Brizinae, Calothecinae, Koeleriinae and Phalaridinae (Poaceae: Pooideae: Poeae: Poeae chloroplast group 1). Phytokeys. <br></div>