Phylogenetic structure in the genus Poa (Poaceae): Progress toward a worldwide infrageneric classification.

SORENG, ROBERT; GILLESPIE, LYNN; GIUSSANI, LILIANA MÓNICA; SCATAGLINI, M. AMALIA; NEGRITO, MARIA

Melbourne

Congreso; XVIII International Botanical Congress; 2011

International Association of Botanical and Mycological Societies (IABMS).

A phylogenetic analysis of Poa L. (over 500 spp.) usingan expanded sample of species from around the world(269 spp. and an additional 39 infraspecies have been examined for plastid and or nrDNA types), with more complete sampling for plastid trn TLF region andnrDNA spacer regions ITS and ETS than previous studies, revealed two large derived clades (number of species based on morphology) subgen. Poa (Poa?Homalopoa; 360 spp.) and subgen. Stenopoa (85 spp.) that contain most of the species in the genus. The subgen. Ochlopoa clade contains a further 36 spp., subgen. Pseudopoa (Eremopoa) 5 spp., subgen. Sylvestres 8 spp.,and sect. Pandemos 2 spp. The small ´N-clade´ had 3 diploid species confined to it by plastid and nrDNA, including the monotypic sect. Nanopoa and two speciesplaced in other non-monophyletic sections, and 11 polyploid species (including all species of sect.Secundae, and some of Glariosae) that share plastid types with it, but ITS?ETS types with the Stenopoa clade. Individuals of Poa bulbosa (sect. Arenariae) had plastid/nrDNA combinations either aligning within the N clade, or within the clade with consectional species in theOchlopoa clade, but no intermixed types. An odd and strongly supported nrDNA ITS?ETS ´X-clade´, for which no corresponding plastid clade has been identified, resolved for 40 species (no diploids known among them) from around the Pacific basin (China, Hawaii, Japan,New Guinea, New Zealand, North and South America: including sects. Acroleucae, Malacanthae,Siphonocoleus, and elements of Orienos, Pauciflorae, and about 2/3 of New Zealand species). Plastid sequences of species with X-type nrDNA mostly resolved in the Poa?Homalopoa clade, but 4 other species aligned with sects. Orienos and Pauciflorae. Based on DNA studies Poa is considered to include the genera Anthochloa, Aphanelytrum, Austrofestuca s.s.,Dissanthelium, Eremopoa, Parodiochloa, Tovarochloa, Tzvelevia; exclude the more recently described genera Arctopoa, Nicoraepoa, Saxipoa, Sylvipoa; and to have reticulate relationships with Aniselytron, Arctopoa, and Nicoraepoa.