Cassiano Aimberê Dorneles Welker

Phylogenetic analysis of Saccharum s.l. (Poaceae; Andropogoneae), with emphasis on the circumscription of the South American species

PREMISE OF THE STUDY Polyploidy and reticulate evolution are often a complication for discovering phylogenetic relationships between genera and species. Despite the huge economic importance of sugarcane (Saccharum officinarum-Poaceae, Andropogoneae), the limits of the genus Saccharum and its species are complex and largely unresolved, involving both polyploidy and reticulate evolution. This study aimed to assess the phylogenetic relationships of Saccharum s.l., including Erianthus and Tripidium, as well as investigate the taxonomic circumscription of the South American species of the genus. METHODS Molecular cloning and sequencing of five regions of four low-copy nuclear loci were performed, including Aberrant panicle organization1 (apo1), Dwarf8 (d8), two exons of Erect panicle2 (ep2-ex7 and ep2-ex8), and Retarded palea1 (rep1). Concatenated trees were reconstructed using Maximum Parsimony, Maximum Likelihood, and Bayesian Inference analyses. KEY RESULTS The allopolyploid origin of Saccharum was demonstrated using evidence from nuclear genes. The samples of Saccharum s.l. grouped in two distinct clades, with S. arundinaceum and S. ravennae (= Tripidium, or Erianthus sect. Ripidium) apart from all other species analyzed of the genus. Saccharum angustifolium, S. asperum, and S. villosum correspond to distinct clades (different species). The plants with intermediate morphology between S. angustifolium and S. villosum presented a pattern of paralogues consistent with a hybrid origin. CONCLUSIONS Saccharum s.l. is polyphyletic and Tripidium should be recognized as a distinct genus. However, no strong evidence was found to support the segregation of Erianthus. The taxonomic circumscription of the South American species of the genus was resolved and the occurrence of natural hybrids was documented. Better understanding of the phylogenetic relationships of Saccharum and relatives may be useful for sugarcane breeders to identify potential taxa for interspecific and intergeneric crosses in the genetic improvement of sugarcane.

The genera Eriochrysis P. Beauv., Imperata Cirillo and Saccharum L. (Poaceae - Andropogoneae - Saccharinae) in the state of Rio Grande do Sul, Brazil

The subtribe Saccharinae belongs to the tribe Andropogoneae and comprises ca. 140 species in 13 genera, including Eriochrysis, Imperata and Saccharum. This work presents a survey of the species of these three genera in the state of Rio Grande do Sul. Intensive field collections were made in different physiographic regions of the state, as well as studies in several herbaria. The occurrence of three native species of each genus was confirmed in Rio Grande do Sul, in addition to sugar cane (Saccharum officinarum) that is cultivated in the region. Based on the material examined, Eriochrysis villosa is reported for the first time in the state of Parana, Brazil. Identification keys for the species, descriptions, data on their geographical distributions, habitats and flowering and fruiting periods, as well as illustrations of important taxonomic characters are provided.

Floristic affinities in montane grasslands in eastern Brazil

The montane grasslands of eastern and southern Brazil occur mostly at elevations above 900 m and are regionally distinguished as campos rupestres and campos de altitude, with the former having a more interior and seasonal climate and the latter a more coastal and humid climate. The floristic relationships between 13 sites of montane grasslands, distributed from north-east to south Brazil (roughly 13–28 °S), were analyzed on the basis of grass species composition. After a compilation of the published literature, the floristic lists were updated according to current taxonomic circumscriptions. The final list had 311 species within 72 genera. The genus Paspalum had the highest number of species (49), whereas 25 genera contained only a single species. Relatively many species (∼50%) were restricted to single study sites, and very few species were widespread. Multivariate analysis supported four groups (bootstrap values >70), primarily distinguishing between seasonal tropical versus humid temperate climates and secondarily between surrounding biomes (caatinga versus cerrado) in the northern tropical sites and geological substrates (granitic versus basaltic) in the southern temperate sites. Our study documents the effects of large-scale climatic and geological factors on the floristic differentiation of montane grasslands and contributes to knowledge of the major vegetation types occurring within Brazilian mountain systems.

A New Species of Isachne (Poaceae, Micrairoideae) from Brazil and a Synopsis of the Brazilian Species of the Genus

Abstract During a survey of the species of Poaceae in Serra do Ouro Branco in the southern Espinhaço Range, State of Minas Gerais, Brazil, a new species of Isachne (I. hirtiglumis) was found and is described here. This new species differs from the other three species of the genus occurring in Brazil mainly by the hirsute indument of the glumes. Isachne hirtiglumis grows in swamps and wet areas associated with gallery forests within the campos rupestres. Besides the description and illustrations, an identification key for the species of Isachne, confirmed for Brazil to date is provided and nomenclatural problems are discussed.

Multilocus phylogeny and phylogenomics of Eriochrysis P. Beauv. (Poaceae–Andropogoneae): Taxonomic implications and evidence of interspecific hybridization ☆

Species delimitation is a vital issue concerning evolutionary biology and conservation of biodiversity. However, it is a challenging task for several reasons, including the low interspecies variability of markers currently used in phylogenetic reconstructions and the occurrence of reticulate evolution and polyploidy in many lineages of flowering plants. The first phylogeny of the grass genus Eriochrysis is presented here, focusing on the New World species, in order to examine its relationships to other genera of the subtribe Saccharinae/tribe Andropogoneae and to define the circumscriptions of its taxonomically complicated species. Molecular cloning and sequencing of five regions of four low-copy nuclear genes (apo1, d8, ep2-ex7 and ep2-ex8, kn1) were performed, as well as complete plastome sequencing. Trees were reconstructed using maximum parsimony, maximum likelihood, and Bayesian inference analyses. The present phylogenetic analyses indicate that Eriochrysis is monophyletic and the Old World E. pallida is sister to the New World species. Subtribe Saccharinae is polyphyletic, as is the genus Eulalia. Based on nuclear and plastome sequences plus morphology, we define the circumscriptions of the New World species of Eriochrysis: E. laxa is distinct from E. warmingiana, and E. villosa is distinct from E. cayennensis. Natural hybrids occur between E. laxa and E. villosa. The hybrids are probably tetraploids, based on the number of paralogues in the nuclear gene trees. This is the first record of a polyploid taxon in the genus Eriochrysis. Some incongruities between nuclear genes and plastome analyses were detected and are potentially caused by incomplete lineage sorting and/or ancient hybridization. The set of low-copy nuclear genes used in this study seems to be sufficient to resolve phylogenetic relationships and define the circumscriptions of other species complexes in the grass family and relatives, even in the presence of polyploidy and reticulate evolution. Complete plastome sequencing is also a promising tool for phylogenetic inference.

New records in Schizachyrium (Poaceae - Andropogoneae) for Rio Grande do Sul and for Brazil

Abstract The genus Schizachyrium Nees includes ca. 60 species, 15 of them previously cited for Brazil. Schizachyrium bimucronatum Roseng., B.R. Arrill. & Izag. is a new record for Brazil and S. lactiflorum (Hack.) Herter, for the State of Rio Grande do Sul. Morphological data to aid in the identification of the two species, including short descriptions and illustrations, as well as data on their geographical distribution and habitat, are provided. Key words : Gramineae, Southern Brazil, taxonomy. Novos registros em Schizachyrium (Poaceae – Andropogoneae) para o Rio Grande do Sul e o Brasil Resumo O genero Schizachyrium Nees inclui cerca de 60 especies, das quais 15 ja foram citadas para o Brasil. Schizachyrium bimucronatum Roseng., B.R. Arrill. & Izag. esta sendo citada pela primeira vez para o Brasil e S. lactiflorum (Hack.) Herter, para o Rio Grande do Sul. Sao fornecidos dados morfologicos para auxiliar na identificacao das duas especies, incluindo breves descricoes e ilustracoes, alem de dados de distribuicao geografica e habitat. Palavras-chave : Gramineae, sul do Brasil, taxonomia.