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The worldwide temperate subtribe Poinae comprises the largest grass genus, Poa (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 tmT-trnL-tmF (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) Poa and (ii) a clade comprising all other sampled Poinae. Nine small genera were nested within the large Poa clade, including Aphanelytrum, Dissanthelium, and Tovarochloa, supporting inclusion of these as sections within Poa. 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 Poa subgenus Arctopoa is incongruent between the two analyses: TLF data support inclusion within Poa and ITS data place it outside of Poa. Similarly, TLF data resolves the genus Aniselytron outside of Poa, whereas ITS data place it within Poa. Based on these results and a consideration of morphology, we recognize Arctopoa and Aniselytron as genera, probably of ancient hybrid origins. Nothogenus xDuarctopoa is coined for Arctopoa x Dupontia, with a single nothospecies xDuarctopoa labradorica. A new combination is provided for Poa subg. Sylvestres. Key words: DNA, hybridization, phylogeny, Poa, Poaceae, Poeae. La sous-tribu des regions temperees mondiales des Poinae comporte les Poa, le plus grand genre d'herbes avec plus de 500 especes, ainsi que de multiples petits genres additionnels. Les auteurs ont explore les limites generiques et les relations au sein des Poinae, en utilisant les donnees de l'espaceur interne transcrit de l'ADN ribosomique nucleique (ITS) et les donnees de sequences plastidiques trnT-trnL-trnF (TFL). Les analyses ITS et TFL concordent generalement quant a la circonscription des genres et aux relations entre les genres de Poinae, mais le dendrogramme des genres est generale ment mieux supporte dans l'arbre ITS a strict consensus. Les ITF et les TFL supportent tous les deux, deux lignees principales de Poinae: (i) Poa et (ii) un clade comportant tous les autres echantillons de Poinae. Neuf petits genres se retrouvent au sein du grand clade Poa, incluant Aphanelytrum, Dissanthelium et Tovarochloa, supportant leur regroupement dans une section les Poa. Dans le second clade, trois sous clades supportent d'etroites relations entre Nicoraepoa, Hookerochloa et Arctagrostis; Arctophila et Dupontia; et Apera, Bellardiochloa et Ventenata. Les genres des sous tribus apparentees Alopecurinae, Cinninae et Miliinae se retrouvent en partie meles avec ou en marge des Poinae de differentes manieres selon les analyses ITS et TFL; et seulement la sous tribu Puccinelliinae trouve un solide support monophyletique. Les analyses ITS supportent la localisation des Catabrosella, Hyalopoa et Paracolpodium dans les Pucinelliinae (aucun TFL disponible). Il n'y a pas de concordance entre les deux analyses pour la position des Poa subg. Arctopoa. De meme, les donnees TFL situent le genre Anisetylon a l'exterieur des Poa, alors que les donnees ITS le placent dans les Poa. Sur la base de ces resultats et des observations morphologiques, les auteurs reconnaissent les Arctopoa et les Aniselytron comme genres, probablement d'origine hybride ancienne. On cree le nothogenre xDuarctopoa, contenant une seule nothoespece xDuarctopoa labradorica. On cree une nouvelle combinaison pour les Poa subg. Sylvestres. Mots-cles : ADN, hybridation, phylogenie, Poa, Poaceae, Poeae. [Traduit par la Redaction], Introduction The large subtribe Poinae and related smaller subtribes Alopecurinae, Cinninae, Miliinae, and Puccinelliinae are widely distributed, cool temperate grasses belonging to tribe Poeae. Together these subtribes include, as currently [...]