Generic boundaries of the African species Panicum deustum Thunb., Panicum trichocladum Hack. ex K. Schum., and Panicum vollesenii Renvoize are analyzed and compared with related genera of the tribe Paniceae and the subtribe Melinidinae. Based on morphological (vegetative and reproductive characters including habit, ligules, inflorescence, spikelets, and ornamentation of the upper anthecium), anatomical (transverse section of leaves), and molecular data (three chloroplast markers), a new genus is proposed for P. deustum, while P. trichocladum and P. vollesenii are transferred to the genus Megathyrsus (Pilg.) B.K. Simon & S.W.L. Jacobs. The phylogenetic position of both taxa within the Melinidinae and their morphological affinities with other genera of the subtribe are also discussed. Additional studies on the Melinidinae will clarify the systematic position of the genera that are still in a doubtful position within the subtribe, such as Eriochloa and Urochloa.

Subtribe Cenchrinae, so-called as the “bristle clade”, is a monophyletic group of panicoid grasses characterized by having sterile branches or bristles on the inflorescences in most of its species. Within this subtribe is also placed Panicum antidotale Retz., an “incertae sedis” species of Panicum L. which lacks bristles along the inflorescence. In this study, we present an update of the subtribe Cenchrinae based on molecular, morphological, and anatomical evidence to clarify the systematic position of P. antidotale in the Cenchrinae, excluding it from Panicum and establishing it in a new genus (i.e., Janochloa Zuloaga & Delfini); the morphological features distinguishing the new genus from other closely related taxa are properly discussed and an identification key to the 24 genera recognized within Cenchrinae is presented. We also add American Setaria species, not tested before, of subgenera Paurochaetium and Reverchoniae, discussing the position of these taxa in actual phylogeny of the genus as well as defining placements in the tree of Setaria species that were imprecisely located in previous analyses. A comparison with the results from other studies, comments on Stenotaphrum Trin. and a brief discussion on conflicting placements in Cenchrus and related taxa, and of Acritochaete Pilg. are also included.

The informal group Caespitosa of Paspalum L. comprises 13–15 perennial species that are able to tolerate extreme climatic stresses, such as prolonged droughts, floods, and saltwater. Previous molecular phylogenetic studies have suggested that the Caespitosa might not be monophyletic, but they did not analyze a large enough sample of taxa for a meaningful conclusion. In this study, we evaluate the phylogeny of the genus Paspalum using parsimony, likelihood, and Bayesian inference based on four DNA regions (ETS, ndhF, rpl16, and trnH-psbA) and increasing the number of sampled species (i.e., a total of 13 taxa and 40 new accessions of the group Caespitosa). Our main objective was to analyze the positions of Caespitosa taxa, assuming a priori that they do not represent a natural group as traditionally circumscribed. Our findings showed the Caespitosa species distributed in seven morphologically distinct clades and correlated with members of the informal groups Alma, Corcovadensia, Dissecta, Lachnea, Macrophylla, Notata, Paniculata, and Rupestria. Clades containing Caespitosa taxa were characterized based on morphological, anatomical, and cytological evidence, one of which was associated with geographic isolation. A comparison with results from other studies, a brief discussion on the group Macrophylla, which our analyses showed to be polyphyletic, and comments on the need for future molecular studies in Paspalum are also included.

A taxonomic revision and nomenclatural update for Paspalum L., group Caespitosa are presented. The group Caespitosa consists of perennial species, usually rhizomatous, with culms simple, erect, inflorescences terminal, pauci-racemose, and spikelets mostly ellipsoid to ovoid or obovoid. It is distributed from the southern United States to northeastern Argentina, with several taxa concentrated in the Caribbean Islands. We recognize 13 species and three varieties (i.e., Paspalum acutifolium León, P. albidulum Henrard, P. bakeri Hack., P. blodgettii Chapm., P. caespitosum Flüggé, P. chacoense Parodi, P. divergens Döll, P. galapageium Chase var. galapageium, P. galapageium var. minoratum Chase, P. galapageium var. redundans (Chase) Delfini & Zuloaga, P. indecorum Mez, P. laxum Lam., P. ligulare Nees, P. molle Poir., and P. redondense Swallen), and designate lectotypes for three names. We propose a new synonym for P. ligulare and a new variety for P. galapageium, and provide updates on inferential lectotypifications (for seven names) and on inferential neotypification (for P. caespitosum var. longifolium). We then comment on four situations of uncertainty, and present new geographic analyses of the species. Illustrations, a key for the species, and additional comments on morphology of the group Caespitosa are also included.

Studies of African material of the tribe Paniceae (Poaceae) resulted in the transfer of 12 species from Panicum, the description of a new species, and the conclusion that the genus Trichanthecium now consists of 52 species. The new Trichanthecium delimitation was confirmed by phylogenetic studies based on chloroplast ndhF and rbcL sequences. Morphological and anatomical characters are discussed within their pylogenetic context. A new species is described: T. marunguensis. Lectotypes are designated for Panicum aequinerve, P. calvum, P. chionachne, P. hochstetteri var. glaberrimum, P. inaequilatum, P. lepidum, P. mokaense, and P. wiehei. The following new combinations are proposed: T. acrotrichum, T. aequinerve, T. calvum, T. chionachne, T. delicatulum, T. eickii, T. hochstetteri, T. inaequilatum, T. perrieri, T. pusillum, T. striatissimum, and T. wiehei. Full synonymies, descriptions, distribution and habitat information, citation of all specimens and a key to the Old World species of the genus are provided; seven species are illustrated.