The Larreoideae subfamily is the major representative of the family Zygophyllaceae in South America, where several of its members are common to dominant in arid regions of the Southern Cone. However, there are currently no phylogenetic analyses of the subfamily that may help to understand its origin and diversification. Additionally, there are taxonomic discrepancies around Bulnesia Gay (1845), one of its more important genera. Accordingly, we performed a phylogenetic analysis combining chloroplast (rbcL and trnL-F) and nuclear (ITS) DNA sequences. Bayesian and Parsimony analyses were performed to highlight the intergeneric relationships within Larreoideae. All genera with the exception of Bulnesia are monophyletic and we propose to redefine Bulnesia, dividing it in two genera. Furthermore, other taxonomic issues of the remaining genera are solved. This study represents the first approximation to clarify the phylogenetic relationships amongst all Larreoideae genera, producing a phylogenetic framework that can be used in future macro-ecological studies.

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.

Otachyriinae Butzin, one of the three subtribes within the Paspaleae tribe of grasses, includes seven genera and approximately 35 species. Interestingly, this subtribe comprises species with C₃, C₃-C₄ intermediate, and C₄ photosynthesis. The circumscription of Otachyriinae has changed through time, and still varies among treatments in current use. The monophyly of this subtribe has been recovered in previous studies based on plastid markers. A phylogenetic study taking into account polyploidy and a low-copy nuclear gene (LCNG) is still lacking in Paspaleae. A phylogeny including data from a LCNG is paramount to uncover reticulated evolution within the group. The purpose of the present study was to reconstruct the evolutionary history of Otachyriinae, based on both chloroplast and LCNG DNA with a focus on polyploidization. Several incongruences between gene trees allowed us to explore relationships between diploid and polyploid taxa. Our study identified several promising topics for future studies: genetic allopolyploidy and autopolyploidy was here documented using the characteristic pattern of double-labelled gene trees. The molecular evidence indicates that at least 40% of species of Otachyriinae show phylogenetic signature of polyploidy (16 taxa appear double-labelled in the nuclear gene trees); furthermore, the results support an allopolyploid origin of at least nine taxa in the subtribe: Rugoloa polygonata, a species with unknown photosynthetic pathway, the proto-kranz species Steinchisma laxum and Rugoloa hylaeica, and the C₃ species Hymenachne felliana, H. grumosa, H. hemitomon, H. donacifolia, H. pernambucense, and P. grande. Also, our results confirm that the C₄ genus Anthaenantia is unambiguously monophyletic and show that Anthaenantia lanata is an autopolyploid. We recognized six genera within subtribe Otachyriinae: Anthaenantia, Hymenachne, Otachyrium, Plagiantha, Rugoloa, and Steinchisma. Finally, Panicum species with historically ambiguous placements, i.e. P. condensatum, P. grande, P. harleyi, P. leptachne, P. longum, and P. stagnatile were transferred to the genus Hymenachne.

— Morphological studies and molecular phylogenetic analyses were carried out to assess the taxonomic status of Hymenophyllum caudiculatum, a species with a disjunct distribution in South America. The species is found in tropical and subtropical forests of Brazil and in temperate forest of southern Argentina and Chile. Based on the results of morphological, molecular, and species delimitation analyses, Hymenophyllum caudatum of the Valdivian forest of southern Chile and Argentina is proposed as a species separate from H. caudiculatum, endemic to Brazil. The two taxa are delimited, respectively, as follows: 1‐5 cm long non-alate stipes (vs. 0.3‐1 cm long non-alate stipes in Brazilian H. caudiculatum); stipe wings gradually ending (vs. stipe wings abruptly ending very near the rhizome); margin entire to somewhat undulate (vs. margin undulate to crispate); soriferous segment alate, angustate, or null (vs. soriferous segment with laminar constriction at apex); and widely obovoid receptacle with sessile sporangia (vs. flattened obovoid or globose receptacle with shortly pedunculated sporangia). Descriptions for the two species recognized here and a map of their geographical distribution are provided, along with nomenclatural revision, illustrations, and conservation status assessments.

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.