Based on recent molecular and morphological studies we present a modern worldwide phylogenetic classification of the AE 12074 grasses and place the 771 grass genera into 12 subfamilies (Anomochlooideae, Aristidoideae, Arundinoideae, Bambusoideae, Chloridoideae, Danthonioideae, Micraioideae, Oryzoideae, Panicoideae, Pharoideae, Puelioideae, and Pooideae), 6 supertribes (Andropogonodae, Arundinarodae, Bambusodae, Panicodae, Poodae, Triticodae), 51 tribes (Ampelodesmeae, Andropogoneae, Anomochloeae, Aristideae, Arundinarieae, Arundineae, Arundinelleae, Atractocarpeae, Bambuseae, Brachyelytreae, Brachypodieae, Bromeae, Brylkinieae, Centotheceae, Centropodieae, Chasmanthieae, Cynodonteae, Cyperochloeae, Danthonieae, Diarrheneae, Ehrharteae, Eragrostideae, Eriachneae, Guaduellieae, Gynerieae, Hubbardieae, Isachneae, Littledaleeae, Lygeeae, Meliceae, Micraireae, Molinieae, Nardeae, Olyreae, Oryzeae, Paniceae, Paspaleae, Phaenospermateae, Phareae, Phyllorachideae, Poeae, Steyermarkochloeae, Stipeae, Streptochaeteae, Streptogyneae, Thysanolaeneae, Triraphideae, Tristachyideae, Triticeae, Zeugiteae, and Zoysieae), and 80 subtribes (Aeluropodinae, Agrostidinae, Airinae, Ammochloinae, Andropogoninae, Anthephorinae, Anthistiriinae, Anthoxanthinae, Arthraxoninae, Arthropogoninae, Arthrostylidiinae, Arundinariinae, Aveninae, Bambusinae, Boivinellinae, Boutelouinae, Brizinae, Buergersiochloinae, Calothecinae, Cenchrinae, Chionachninae, Chusqueinae, Coicinae, Coleanthinae, Cotteinae, Cteniinae, Cynosurinae, Dactylidinae, Dichantheliinae, Dimeriinae, Duthieinae, Eleusininae, Eragrostidinae, Farragininae, Germainiinae, Gouiniinae, Guaduinae, Gymnopogoninae, Hickeliinae, Hilariinae, Holcinae, Hordeinae, Ischaeminae, Loliinae, Melinidinae, Melocanninae, Miliinae, Monanthochloinae, Muhlenbergiinae, Neurachninae, Olyrinae, Orcuttiinae, Oryzinae, Otachyriinae, Panicinae, Pappophorinae, Parapholiinae, Parianinae, Paspalinae, Perotidinae, Phalaridinae, Poinae, Racemobambosinae, Rottboelliinae, Saccharinae, Scleropogoninae, Scolochloinae, Sesleriinae, Sorghinae, Sporobolinae, Torreyochloinae, Traginae, Trichoneurinae, Triodiinae, Tripogoninae, Tripsacinae, Triticinae, Unioliinae, Zizaniinae, and Zoysiinae). In addition, we include a radial tree illustrating the hierarchical relationships among the subtribes, tribes, and subfamilies. We use the subfamilial name, Oryzoideae, over Ehrhartoideae because the latter was initially published as a misplaced rank, and we circumscribe Molinieae to include 13 Arundinoideae genera. The subtribe Calothecinae is newly described and the tribe Littledaleeae is new at that rank.

We present a new worldwide phylogenetic classification of 11 506 grass species in 768 genera, 12 subfamilies, seven supertribes, 52 tribes, five supersubtribes, and 90 subtribes; and compare two phylogenetic classifications of the grass family published in 2015 (Soreng et al. and Kellogg). The subfamilies (in descending order based on the number of species) are Pooideae with 3968 species in 202 genera, 15 tribes, and 30 subtribes; Panicoideae with 3241 species in 247 genera, 13 tribes, and 19 subtribes; Bambusoideae with 1670 species in 125 genera, three tribes, and 15 subtribes; Chloridoideae with 1602 species in 124 genera, five tribes, and 26 subtribes; Aristidoideae with 367 species in three genera, and one tribe; Danthonioideae with 292 species in 19 genera, and one tribe; Micrairoideae with 184 species in eight genera, and three tribes; Oryzoideae with 115 species in 19 genera, four tribes, and two subtribes; Arundinoideae with 40 species in 14 genera, two tribes, and two subtribes; Pharoideae with 12 species in three genera, and one tribe; Puelioideae with 11 species in two genera, and two tribes; and the Anomochlooideae with four species in two genera, and two tribes. We also include a radial tree illustrating the hierarchical relationships among the subtribes, tribes, and subfamilies. Newly described taxa include: supertribes Melicodae and Nardodae; supersubtribes Agrostidodinae, Boutelouodinae, Gouiniodinae, Loliodinae, and Poodinae; and subtribes Echinopogoninae and Ventenatinae.

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Abstract.Evidence for global warming is inferred from spring advances in first-flowering in plants. The trend of average first-flowering times per year for the study group shows a significant advance of 2.4 days over a 30-year period. When 11 species that exhibit later first-flowering times are excluded from the data set, the remaining 89 show a significant advance of 4.5 days. Significant trends for earlier-flowering species range from •3.2 to •46 days, while those for later-flowering species range from -1-3.1 to -1-10.4 days. Advances of first-flowering in these 89 species are directly correlated with local increase in minimum temperature (Tf^in).

Circumscriptions of and relationships among many genera and suprageneric taxa of the diverse grass tribe Poeae remain controversial. In an attempt to clarify these, we conducted phylogenetic analyses of >2400 new DNA sequences from two nuclear ribosomal regions (ITS, including internal transcribed spacers 1 and 2 and the 5.8S gene, and the 3’-end of the external transcribed spacer (ETS)) and five plastid regions (matK, trnL–trnF, atpF–atpH, psbK–psbI, psbA–rps19–trnH), and of more than 1000 new and previously published ITS sequences, focused particularly on Poeae chloroplast group 1 and including broad and increased species sampling compared to previous studies. Deep branches in the combined plastid and combined ITS+ETS trees are generally well resolved, the trees are congruent in most aspects, branch support across the trees is stronger than in trees based on only ITS and fewer plastid regions, and there is evidence of conflict between data partitions in some taxa. In plastid trees, a strongly supported clade corresponds to Poeae chloroplast group 1 and includes Agrostidinae p.p., Anthoxanthinae, Aveninae s.str., Brizinae, Koeleriinae (sometimes included in Aveninae s.l.), Phalaridinae and Torreyochloinae. In the ITS+ETS tree, a supported clade includes these same tribes as well as Sesleriinae and Scolochloinae. Aveninae s.str. and Sesleriinae are sister taxa and form a clade with Koeleriinae in the ITS+ETS tree whereas Aveninae s.str. and Koeleriinae form a clade and Sesleriinae is part of Poeae chloroplast group 2 in the plastid tree. All species of Trisetum are part of Koeleriinae, but the genus is polyphyletic. Koeleriinae is divided into two major subclades: one comprises Avellinia, Gaudinia, Koeleria, Rostraria, Trisetaria and Trisetum subg. Trisetum, and the other Calamagrostis/Deyeuxia p.p. (multiple species from Mexico to South America), Peyritschia, Leptophyllochloa, Sphenopholis, Trisetopsis and Trisetum subg. Deschampsioidea. Graphephorum, Trisetum cernuum, T. irazuense and T. macbridei fall in different clades of Koeleriinae in plastid vs. nuclear ribosomal trees, and are likely of hybrid origin. ITS and matK trees identify a third lineage of Koeleriinae corresponding to Trisetum subsect. Sibirica, and affinities of Lagurus ovatus with respect to Aveninae s.str. and Koeleriinae are incongruent in nuclear ribosomal and plastid trees, supporting recognition of Lagurus in its own subtribe. A large clade comprises taxa of Agrostidinae, Brizinae and Calothecinae, but neither Agrostidinae nor Calothecinae are monophyletic as currently circumscribed and affinities of Brizinae differ in plastid and nuclear ribosomal trees. Within this clade, one newly identified lineage comprises Calamagrostis coarctata, Dichelachne, Echinopogon (Agrostidinae p.p.) and Relchela (Calothecinae p.p.), and another comprises Chascolytrum (Calothecinae p.p.) and Deyeuxia effusa (Agrostidinae p.p.). Within Agrostidinae p.p., the type species of Deyeuxia and Calamagrostis s.str. are closely related, supporting classification of Dey...

The systematics of grasses has advanced through applications of plastome phylogenomics, although studies have been largely limited to subfamilies or other subgroups of Poaceae. Here we present a plastome phylogenomic analysis of 250 complete plastomes (179 genera) sampled from 44 of the 52 tribes of Poaceae. Plastome sequences were determined from high throughput sequencing libraries and the assemblies represent over 28.7 Mbases of sequence data. Phylogenetic signal was characterized in 14 partitions, including (1) complete plastomes; (2) protein coding regions; (3) noncoding regions; and (4) three loci commonly used in single and multi-gene studies of grasses. Each of the four main partitions was further refined, alternatively including or excluding positively selected codons and also the gaps introduced by the alignment. All 76 protein coding plastome loci were found to be predominantly under purifying selection, but specific codons were found to be under positive selection in 65 loci. The loci that have been widely used in multi-gene phylogenetic studies had among the highest proportions of positively selected codons, suggesting caution in the interpretation of these earlier results. Plastome phylogenomic analyses confirmed the backbone topology for Poaceae with maximum bootstrap support (BP). Among the 14 analyses, 82 clades out of 309 resolved were maximally supported in all trees. Analyses of newly sequenced plastomes were in agreement with current classifications. Five of seven partitions in which alignment gaps were removed retrieved Panicoideae as sister to the remaining PACMAD subfamilies. Alternative topologies were recovered in trees from partitions that included alignment gaps. This suggests that ambiguities in aligning these uncertain regions might introduce a false signal. Resolution of these and other critical branch points in the phylogeny of Poaceae will help to better understand the selective forces that drove the radiation of the BOP and PACMAD clades comprising more than 99.9% of grass diversity.

We conducted a molecular phylogenetic study of the tribe Stipeae using nine plastid DNA sequences (trnK‐matK, matK, trnH‐psbA, trnL‐F, rps3, ndhF, rpl32‐trnL, rps16‐trnK, rps16 intron), the nuclear ITS DNA regions, and micromorphological characters from the lemma surface. Our large original dataset includes 156 accessions representing 139 species of Stipeae representing all genera currently placed in the tribe. The maximum likelihood and Bayesian analyses of DNA sequences provide strong support for the monophyly of Stipeae; including, in phylogenetic order, Macrochloa as remote sister lineage to all other Stipeae, then a primary stepwise divergence of three deep lineages with a saw‐like (SL) lemma epidermal pattern (a plesiomorphic state). The next split is between a lineage (SL1) which bifurcates into separate Eurasian and American clades, and a lineage of three parts; a small Patis (SL2) clade, as sister to Piptatherum s.str. (SL3), and the achnatheroid clade (AC). The AC exhibits a maize‐like lemma epidermal pattern throughout. AC consists of a core clade of Austral‐Eurasian distribution and a “major American clade” of North and South American distribution. The base chromosome number for Stipeae is somewhat ambiguous but based on our survey it seems most likely to be x = 11 or 12. Our phylogenetic hypothesis supports the recognition of the following genera and groups (listed by region): Eurasia—Achnatherum, “Miliacea group”, “Neotrinia” (monotypic), Orthoraphium (monotypic), Patis (also 1 from North America), Piptatherum s.str., Psammochloa (monotypic), Ptilagrostis, Stipa, “Timouria group”, and Trikeraia; Mediterranean—Ampelodesmos (monotypic), Celtica (monotypic), Macrochloa (monotypic), and “Stipella‐Inaequiglumes group”; Australasia—Anemanthele (monotypic), and Austrostipa; North America (NA)—“Eriocoma group”, Hesperostipa, Oryzopsis (monotypic), Piptatheropsis, “Pseudoeriocoma group”, and “Stillmania” (monotypic); South America—Aciachne, Amelichloa (also NA), Anatherostipa (s.str.), Jarava (polyphyletic), Lorenzochloa, Nassella (also NA), Ortachne, Pappostipa (also NA), and Piptochaetium (also NA). Monophyly of Phaenospermateae including Duthieinae is demonstrated, and its inclusion within or treatment as sister to Stipeae is rejected.