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.

Included in the PACMAD clade of the family Poaceae (Panicoideae, Arundinoideae, Chloridoideae, Micrairoideae, Aristidoideae, Danthonioideae), the tribe Paniceae s.l. is one of the largest tribes of the subfamily Panicoideae, with more than 2000 species. This tribe comprises a huge morphological, cytological and physiological diversity represented by different inflorescence types, several basic chromosome numbers, and at least four major photosynthetic pathways. The tribe Paniceae has been the subject of molecular studies that have confirmed its paraphyly: two major clades were recognized based on their basic chromosome numbers (x = 9, x = 10). The x = 10 Paniceae clade is sister to the Andropogoneae-Arundinelleae s.s. clade (x = 10), while the combined x = 10 clade is sister to the x = 9 clade that contains the remaining genera of Paniceae. As a result of a recent realignment within the tribe in terms of the phylogenetic position of minor and major Paniceae genera, a reanalysis of the whole sampling is performed and new underrepresented taxa are discussed. A total of 155 genera, currently considered within subfamily Panicoideae, are represented here by almost all genera of Paniceae s.l., representatives of Andropogoneae and Arundinelleae s.s., and the endemic and small tribe Steyermarkochloeae; we also included specimens of subfamily Micrairoideae, tribes Isachneae and Eriachneae. The sampling includes as outgroups 18 genera of the PACMAD clade (excluding Panicoideae) and four genera from the BEP clade (Bambusoideae, Ehrhartoideae, Pooideae), rooting with Bromus inermis. A matrix with 265 taxa based on the combined evidence from ndhF plastid sequences (2074 bp) and 57 morphological characters was subjected to parsimony analyses. Jackknife resampling was used to calculate group support. Most clades are characterized by morphological, cytological, anatomical, and ⁄ or physiological characters. Major tribal changes are based on the basic chromosome number; the pantropical x = 9 clade is here recognized as Paniceae s.s., while the American x = 10 Paniceae s.l. is restricted to the reinstated tribe Paspaleae. The optimization of the photosynthetic pathway for the Paspaleae-Andropogoneae-Arundinelleae s.s. clade, including the monotypic Reynaudia, shows a plesiomorphic C 4 state while the ancestral state for Paniceae s.s. is ambiguous. If Reynaudia were not included or placed elsewhere, the ancestral photosynthetic pathway for both the Paspaleae-Andropogoneae-Arundinelleae s.s. clade and the Paniceae s.s. would be unambiguously C 3 . In order to explore character evolution further, the morphological characters were mapped onto one of the most parsimonious trees. A relationship between photosynthetic pathways and inflorescence morphology is suggested here for the first time. Based on the optimization of morphological characters and additional data, we propose names for almost all inner clades at the rank of subtribe with a few groups as incertae sedis. With this extensive sampling, we resolved the phylogenetic relations...

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Due to the consistency between the present results and different phylogenetic hypotheses (including morphological, developmental and multilocus approaches), and the high support found for the PCO clade, also including the type species of the three genera, we propose unification of Pennisetum, Cenchrus and Odontelytrum. Species of Pennisetum and Odontelytrum are here transferred into Cenchrus, which has priority. Sixty-six new combinations are made here.

The distribution data of 340 grass species sampled in a region of 53.219 km 2 in the northwestern corner of Argentina (between $21°S and $24°S) were analyzed to search for concordance in species distributions by using the program NDM ⁄ VNDM. Here, the traditional biogeographic hypothesis proposed for the region is evaluated for the first time by using a quantitative method and an optimal criterion specifically developed within the context of areas of endemism. Three different grid sizes (0.5°· 0.5°, 0.35°· 0.35°a nd 0.2°· 0.2°) were used to analyze three nested data sets: species found in the Andes of Argentina, Bolivia and ⁄ or Chile; Andean distributed species; and all grass species found in the study region. The main areas supported by the analyses correspond generally to the traditional biogeographic hypothesis proposed for the region. Local distribution patterns defined by species restricted to the study region were best supported under the small grid sizes, while the bigger grid sizes recovered areas defined by species with a broader distribution. The local distribution patterns emerged in all the analyses even when widespread species were added to the data set.

AjiSriiACI'r\v ('nt\-(i\(' sppt'ies are tit'aU'[)(M-h-ninia not enclosing llu-t4> of the upper palea. Speeies ^rovs in Soutli Aineriea from Mexico to Argentina and Uruguay. A ehulistic analysis of suhgenus Crrrsia was conducted iu test its nionophyly. and to eslahlish ils relaliorislii[) willi other groujis u{ PasfHilum. A key to the speeies in sul)genus Crrrsia is given, as well as nior[)hoh)gical desi-riplion and illustration, and dislrihulion maps. kry fvifnls: America, Crrrsia, eladislies, Paspalnm. [\taeeae. /^/.s/>^////;n I., iiuludes a])[)roxiiiiat(dy 330 speeies ///// .suLg. Ceresia, eonsideniig; ve*i;etati\e and re- (lislril)ule(l in Lropieal and suhhopieal regions of prodnelive characters, analyzing hahilal and distri-Arn<'rica, with a few taxa growing in the Old World hution range. A cladi.slic analysis was furdicr p<^r- (Claylon & Kcnvoize, 19{56). Dne to its large iiuin-lornied in order to Icsl the monophyly of the bcr of s()ccies, and the tnorphidogical variali<»n snhgenus and to estahlisli the relationships of its present within the g(MUJs, PdsjHihim has been divided into suhgenera. sections, or iidornial groups mainly on the basis of morphological characters, such as infloresctMice type or features of the spikelet (Nees. 1829: Doidl. ir»77: Chase. 1927: Pilger. 1929 Clayton .^ Kenvoize, 19J56; Morrone ct ah. 1995 Morrone ct ah. , 1996, 2()()(); CialdeHa el ah, 1995). species llisiomCerrsia was estahlisluMl a! the g;enerle level hy Persoon (lo05-lo()7). on the basis <»f C. clci^dDs (P dspdhim memfmnHicciun Lam., non Walt., 17oo). StibscHjuenlly, Kcichetd)acdt treated Ccrcsia as a Chase (1929) divided Paspalum into subgenera subgenus of Paspalum (Chase, 1929). Several spe-Paspalum and Ccrcsia (Pers.) I{chb., characterizing ries were described in Cercsia in the 19th cenliny (riiigge, 1810; Trinius, 1826 Trinius, . 1828 Trinius, -1836 Ne(^s, 1829; Doell, 1877). N

The genus Setaria is the largest genus in the so-called bristle clade, a monophyletic group of panicoid grasses distinguished by the presence of sterile branches, or bristles, in their inflorescences. The clade includes both foxtail millet and pearl millet, the latter an important cereal crop in dry parts of the world. Other members of the clade are weeds that are widespread agricultural pests. Previous molecular phylogenetic studies have suggested that Setaria might not be monophyletic but did not have a large enough sample of species to test this rigorously. In addition, taxonomic studies have suggested a close relationship between Setaria and Paspalidium, with some authors combining them into a single genus, but molecular studies included too few Paspalidium accessions for a meaningful conclusion. Accordingly, we have produced 77 new sequences of the chloroplast gene ndhF for 52 species not in previous analyses. These were added to available sequences for 35 species in 10 genera of the bristle clade and four outgroup taxa. We find that Setaria species fall into several moderately to strongly supported clades that correlate with geography but not with the existing subgeneric classification. Relationships among these clades and among other genera within the bristle clade are unclear. Constraint experiments using the approximately unbiased test reject the monophyly of Pennisetum, Setaria, and Setaria plus Paspalidium, as well as several other groupings, although the test may be overly sensitive and prone to Type I error. The more conservative Shimodaira-Hasegawa test fails to reject monophyly of any of the tested clades.

Phylogenetic analyses of 131 terminals of Paspalum and related genera, based on both plastid and nuclear markers, were performed under maximum parsimony and Bayesian methods. The total evidence analyses generated a hypothesis showing that Paspalum would be monophyletic if Spheneria, Thrasyopsis and Reimarochloa are included within the genus. Paspalum inaequivalve and P. microstachyum, two species of the Inaequivalvia group were related to genus Anthaenantiopsis, excluded from Paspalum, or nested within it by plastid and nuclear markers, respectively. Subgenera Anachyris and Harpostachys were partially recovered as monophyletic assemblages, while subg. Ceresia and Paspalum resolved as polyphyletic. Within subgenus Paspalum, some informal groups were recovered as monophyletic, while others were resolved as paraphyletic or polyphyletic. Phylogenetic relationships among species of Paspalum were partially recovered possibly due to reticulation events among species, autopolyploidization and apomixis; all these processes being common in Paspalum, thus obscuring the infrageneric classification.