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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Dated molecular phylogenetic trees show that the Andean uplift had a major impact on South American biodiversity. For many Andean groups, accelerated diversification (radiation) has been documented. However, not all Andean lineages appear to have diversified following the model of rapid radiation, particularly in the central and southern Andes. Here, we investigated the diversification patterns for the largest South American-endemic lineage of Brassicaceae, composed of tribes Cremolobeae, Eudemeae and Schizopetaleae (CES clade). Species of this group inhabit nearly all Andean biomes and adjacent areas including the Atacama-Sechura desert, the Chilean Matorral and the Patagonian Steppe. First, we studied diversification times and historical biogeography of the CES clade. Second, we analysed diversification rates through time, lineages and associated life forms. Results demonstrate that early diversification of the CES clade occurred in the early to mid-Miocene (c. 12-19 Mya) and involved the central Andes, the southern Andes and the Patagonian Steppe, and the Atacama-Sechura desert. The Chilean Matorral and northern Andes were colonized subsequently in the early Pliocene (4-5 Mya). Diversification of the CES clade was recovered as a gradual process without any evidence for rate shifts or rapid radiation, in contrast to many other Andean groups analysed so far. Diversification time/rates and biogeographical patterns obtained for the CES clade are discussed and compared with patterns and conclusions reported for other Andean plant lineages.

© The Willi Hennig Society 2010. Abstract The tribe Stipeae, with nearly 550 species, includes 28 core genera, of which 13 occur in America: Achnatherum, Aciachne, Amelichloa, Anatherostipa, Hesperostipa, Jarava, Nassella, Ortachne, Oryzopsis, Pappostipa, Piptatherum, Piptochaetium and Ptilagrostis. Based on 37 species representing 14 Stipeae genera, and using four chloroplast markers and morphological characters, we provide a phylogenetic hypothesis of the New World Stipeae, with our focus on Amelichloa and Aciachne. Parsimony analyses included two approaches: (i) a multiple‐sequence alignment where gaps were treated as missing or coded, (ii) using direct sequences by direct optimization as implemented by the program POY v.4.0.2870. Analyses under direct optimization were conducted using the molecular data sets independently and combined, and with morphological data. Different cost regimes were explored and the one producing the highest congruence between partitions was chosen. Among the genera considered, only Piptochaetium, Austrostipa, and Hesperostipa were resolved as monophyletic, while Achnatherum, Amelichloa s.l., Anatherostipa, Jarava and Nassella were polyphyletic, and Aciachne was polyphyletic or paraphyletic. As a result, Amelichloa can be restricted to a monophyletic group if including A. brachychaeta, A. ambigua, A. clandestina and A. caudata, or it should be considered within Nassella. The phylogenetic position of species of Aciachne suggests inbreeding and outbreeding events with species of Anatherostipa, Ortachne and Hesperostipa.

Panicum sensu stricto is a genus of grasses (Poaceae) with nearly, according to this study, 163 species distributed worldwide. This genus is included in the subtribe Panicinae together with Louisiella, the latter with 2 species. Panicum and subtribe Panicinae are characterized by including annual or perennial taxa with open and lax panicles, and spikelets with the lower glume reduced; all taxa also share a basic chromosome number of x = 9 and a Kranz leaf blade anatomy typical of the NAD-me subtype photosynthetic pathway. Nevertheless, the phylogenetic placements of many Panicum species, and the circumscription of the genus, remained untested. Therefore, phylogenetic analyses were conducted using sequence data from the ndhF plastid region, in an extensive worldwide sampling of Panicum and related genera, in order to infer evolutionary relationships and to provide a phylogenetic framework to review the classification of the genus. Diversification times, historical biogeography and evolutionary patterns of the life history (annual vs. perennial) in the subtribe and Panicum were also studied. Results obtained provide strong support for a monophyletic Panicum including 71 species and 7 sections, of which sections Arthragrostis and Yakirra are new in the genus; 7 new combinations are made here. Furthermore, 32 species traditionally assigned to Panicum were excluded from the genus, and discussed in other subtribes of Paniceae. Our study suggested that early diversification in subtribe Panicinae and Panicum occurred through the Early-Mid Miocene in the Neotropics, while the subsequent diversification of its sections mainly occurred in the Late Miocene-Pleistocene, involving multiple dispersals to all continents. Our analyses also showed that transition rates and changes between annual and perennial life history in Panicum were quite frequent, suggesting considerable lability of this trait. Changes of the life history, together with C4 photosynthesis, and the multiple dispersal events since the Mid Miocene, seem to have facilitated a widespread distribution of the genus. All these findings contribute to a better understanding of the systematics and evolution of Panicum.

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Rupichloa, a new genus of Paniceae restricted to Bahia and Minas Gerais, Brazil, and including two species, R. acuminata and R. decidua, is here described on the basis of morphological and molecular characters. Analyses of DNA sequence data from plastid rpl16 and ndhF indicate that the two included species do not belong to Urochloa, in which they were previously placed. The affinities of the new genus with other genera of Paniceae are discussed.

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