Phylogenetic relationships in subtribe Poinae (Poaceae, Poeae) based on nuclear ITS and plastid trnT-trnL-trnF sequences

The worldwide temperate subtribe Poinae comprises the largest grass genus. Poo (500+ species), and Multiple additional small genera. We explore generic boundaries and relationships among genera of Poinae using nuclear ribosomal internal transcribed spacer data (ITS) and plastid trnT-trnL-trnF (TLF) sequence data. ITS and TLF analyses are mostly congruent with regards to circumscription of genera, and with respect to relationships among Poinae genera. but tree structure is generally better supported among genera in the ITS strict consensus tree. ITS and TLF both Support two main Poinae lineages: (i) Poo and (ii) a clade comprising all other sampled Poinae. Nine small genera were nested within the large Poo clade, including Aphanelytrum. Dissanthelium, and Tovarochloa. supporting inclusion of these as sections within Poo. In the second clade, three subclades support close relationships among Nicoraepoa, Hookerochloa. and Arctagrostis; Arctophila and Dupontia: and Apera, Bellardiochloa. and Ventenata. Genera of the related subtribes Alopecurinae, Cinninae. and Miliinae were mixed among or in Part external to Poinae in different ways in ITS and TLF analyses. and only subtribe Puccinelliinae was strongly supported and monophyletic. ITS analyses Supported placement of Catabrosella, Hyalopoa, and Paracolpodium in Puccinelliinae (no TLF data available). The position of Poo subgenus Arctopoa is inconguent between the two analyses: TLF data Support inclusion within Poo and ITS data place it outside of Poo. Similarly. TLF data resolves the genus Aniselytron Outside of Poo. whereas ITS data place it within Poo. Based oil these results and a consideration of morphology, we recognize Arctopoa and Aniselytron its genera, probably of ancient hybrid origins. Nothogenus x Duarctopoa is coined for Arctopoa x Dupontia. with a single nothospecies x Duarctopoa labradorica. A new combination is provided for Poo subg. Sylvestres.