Myriam Carolina Peichoto

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.

Morphometric analysis of Schizachyrium condensatum (Poaceae) and related species

Our aim was to assess the degree of morphological differentiation of a group of taxa of Schizachyrium Nees, which presents similar inflorescences and shares habitat and geographic areas: Schizachyrium bimucronatum, S. condensatum, S. lactiflorum, S. microstachyum subsp. microstachyum, S. microstachyum subsp. elongatum, and S. plumigerum. To accomplish this purpose, 22 exomorphological traits were analyzed using multivariate methods. The results obtained support the identity of Schizachyrium condensatum and related species as independent taxa. In addition, the analysis evidences the reliability of several inflorescence characters, which had not been previously considered in the identification of the different taxa. Based upon the information obtained, a new identification key for these taxa was constructed.

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.

Nuevos taxones para el género Schizachyrium (Poaceae: Andropogoneae) del Noroeste de la Argentina y Bolivia

ResumenDos nuevos taxones, Schizachyrium paucispiculatum y Schizachyrium hatschbachii subsp. saltense, son descritos e ilustrados. Se presentan los caracteres diagnósticos, comentarios taxonómicos y sus relaciones con especies afines.AbstractTwo new taxa, Schizachyrium paucispiculatum and Schizachyrium hatschbachii subsp. saltense, are described and illustrated. Diagnostic characters, taxonomic comments, and discussions of relationships of these taxa with other species are provided.

Identity of Schizachyrium sulcatum and S. brevifolium (Poaceae: Andropogoneae)

Schizachyrium sulcatum, distributed in Brazil, Bolivia and Colombia, is described, illustrated, and reported for the first time from Peru and Venezuela. Synonymy, geographical distribution, ecology, and a list of representative specimens examined are provided. Characters of taxonomic value are established in order to differentiate this species fromS. brevifolium. A comparative study based on morphology, leaf anatomy, and micromorphological features of the spikelets and leaf blade are included. The multivariate analysis based on morphological variables allowsS. sulcatum to be distinguished clearly fromS. brevifolium.

A New Allopolyploid Species of Saccharum (Poaceae - Andropogoneae) from South America, with Notes on Its Cytogenetics

Abstract Allopolyploidy is a major mode of speciation in flowering plants and particularly in the grass tribe Andropogoneae, which includes sugarcane (Saccharum officinarum) and relatives. A new species of Saccharum from South America (S. intermedium) is described here, supported by morphological, molecular and cytogenetic evidence. Previous molecular analyses indicated an allopolyploid origin of the new species through interspecific hybridization between S. angustifolium and S. villosum. The new taxon has intermediate morphology between the two parental species. Cytogenetic analyses of the three species were performed, including chromosome counts, meiotic regularity, and pollen viability and morphology. The new taxon is hexaploid (2n = 60), while the parental species are triploids (2n = 30), confirming the ploidy level suggested by the number of paralogues in phylogenetic trees based on low-copy nuclear genes. This represents the first chromosome count for S. intermedium and a new cytotype for S. villosum. Although both parental species are triploids, they surprisingly exhibited regular meiosis and high pollen viability, indicating they are male-fertile, as is the hexaploid new species. Data on geographic distribution and phenology is also presented, aswell as a key for the South American species of Saccharum.

Morphometric Analysis of Schizachyrium (Poaceae—Andropogoneae) Reveals Two New Species from South America

Abstract Schizachyrium (Poaceae—Andropogoneae) includes ca. 60 species distributed in tropical and subtropical regions of the world. Although the genus has been revised recently for South America, a group of specimens with intermediate traits from Cerrado vegetation of Brazil and Paraguay was found. The aim of this paper is to assess the morphological variation of these specimens to clarify their taxonomic identity. Thirty-seven traits (15 qualitative and 22 quantitative characters) were analyzed using multivariate methods (cluster and principal coordinate analysis). The analysis included specimens from Central Brazil and Paraguay, as well as the type material of several morphologically similar species. The results obtained showed that the samples investigated form two clearly distinct groups from the species hitherto recognized. Based on this morphometric analysis, two new species of Schizachyrium from South America are proposed, one of them occurring in Brazil and Paraguay (Schizachyrium angustispiculatum), and the other restricted to Brazil (S. vallsii). Moreover, Andropogon luxurians proved as a distinct taxon from Schizachyrium sanguineum, being proposed the new combination of the name for the genus Schizachyrium (S. luxurians). Descriptions and illustrations of the two new species and the new combination are presented, as well as a key to separate them from other morphologically related species.

New taxa for the genus Schizachyrium (Poaceae: Andropogoneae) of Northwestern Argentina and Bolivia.

ResumenDos nuevos taxones, Schizachyrium paucispiculatum y Schizachyrium hatschbachii subsp. saltense, son descritos e ilustrados. Se presentan los caracteres diagnósticos, comentarios taxonómicos y sus relaciones con especies afines.AbstractTwo new taxa, Schizachyrium paucispiculatum and Schizachyrium hatschbachii subsp. saltense, are described and illustrated. Diagnostic characters, taxonomic comments, and discussions of relationships of these taxa with other species are provided.

Nuevos taxones para el género Schizachyrium

ResumenDos nuevos taxones, Schizachyrium paucispiculatum y Schizachyrium hatschbachii subsp. saltense, son descritos e ilustrados. Se presentan los caracteres diagnósticos, comentarios taxonómicos y sus relaciones con especies afines.AbstractTwo new taxa, Schizachyrium paucispiculatum and Schizachyrium hatschbachii subsp. saltense, are described and illustrated. Diagnostic characters, taxonomic comments, and discussions of relationships of these taxa with other species are provided.