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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.

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Recebido em 30/7/96. Aceito em 23/12/96.

ResumoÉ apresentada uma revisão taxonômica das espécies de Andropogon L. que ocorrem no Brasil com base em coletas, observação de populações no campo e análise de coleções de 72 herbários nacionais e internacionais. Foram confirmadas 28 espécies, incluindo A. gayanus Kunth, introduzida da África para cultivo, além de uma subespécie e uma variedade. O trabalho inclui chaves de identificação, descrições e ilustrações para todos os táxons, além de dados sobre distribuição geográfica, hábitat, período de floração, nomenclatura e comentários gerais. Palavras-chave: Gramineae, taxonomia. AbstractA taxonomic revision of the genus Andropogon L. in Brazil is presented. Based on field collections, observation of the populations and revision of 72 national and international herbaria, 28 species, including A. Gayanus Kunth introduced from Africa were confirmed, besides one subspecie and one variety. The work includes key for the identification of the confirmed taxa, descriptions and illustrations, as well as data about geographic distribution, habitat, flowering periods, typification, synonymy and general comments.

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.