Nicolás Nagahama

Review of the Genus Andropogon (Poaceae: Andropogoneae) in America Based on Cytogenetic Studies

Andropogon is a pantropical grass genus comprising 100–120 species and found mainly in the grasslands of Africa and the Americas. In the new world the genus is represented by approximately sixty (diploids or hexaploids) species grouped in three sections. The hexaploid condition occurs only in the Americas and the full process of this origin is still uncertain, although cytogenetic analysis coupled with taxonomic evidence have provided strong support for new hypothesis. Stebbins proposed the first hypothesis suggesting that the origin of polyploidy in species of Andropogon in North America resulted from duplication of the genome of some diploid species, and then by intergeneric crosses with species of a related genus. Since then, numerous studies were performed to clarify the evolutionary history of the genus in America. In this paper, we present a review of cytogenetic studies in the American Andropogon species during the last four decades.

Taxon Delimitation in the Andropogon lateralis Complex (Poaceae) in Southern South America based on Morphometrical Analyses

Abstract In the tribe Andropogoneae, morphological variation is remarkable, mainly in the inflorescence on the pair of spikelets which are the core elements of the inflorescence. The genus Andropogon includes the Andropogon lateralis complex, which is distributed primarily in South and Central America, comprising approximately twelve taxa and inter-specific hybrids. The aim of this study was to assess morphological variation in the A. lateralis complex through morphometric analyses of specimens from natural populations. For this purpose, univariate ANOVA, as well as principal component analysis and discriminant analysis of 19 morphological variables of synflorescences were performed, revealing differences between species and interspecific hybrids. The selected diagnostic traits of species and hybrids based on quantitative characters of the synflorescences provided a valuable tool for taxonomic studies in the genus. The results obtained made it possible to generate the first identification key that includes both species and hybrids of the A. lateralis complex for South America.

Valeriana gaimanensis (Valerianaceae nom. conserv.), a New Species from the Patagonian Semi-Arid Desert, Argentina

Abstract Valeriana gaimanensis, a new species from Argentinean Patagonia, is described and illustrated. The new species belongs to the subgenus Valeriana and is apparently endemic to the Extra-Andean Patagonia region, where it grows in an extremely arid environment, in contrast to most Valeriana species distributed in Patagonia. The morphological relationships of V. gaimanensis are discussed in comparison with V. carnosa, which resembles the new species morphologically. Principal component analysis was performed with 28 morphological variables, including specimens of these two species, revealing differences between them. This study provides the distribution, habitat, phenology, and etymology of V. gaimanensis, as well as a key separating it from the other Valeriana species that inhabit Extra-Andean Patagonia.

ANDROPOGON × PARAGUARIENSIS, A NEW NAME FOR ANDROPOGON × VELUTINUS (POACEAE, ANDROPOGONEAE)

The new name Andropogon × paraguariensis Norrmann & Nagahama is proposed to replace the illegitimate name Andropogon × velutinus Norrmann & Nagahama, a natural hybrid from southern South America.

NOMBRES VÁLIDOS PARA HÍBRIDOS DEL COMPLEJO ANDROPOGON LATERALIS (POACEAE, ANDROPOGONEAE) SOBRE LA BASE DE ANÁLISIS MULTIVARIADOS

The Andropogon lateralis complex is constituted by 13 taxonomic entities: seven species and six class inter-specific hybrids distributed in Central and South America. Natural hybrids within this group are quite common due to lack of inter-specific barriers. These hybrids have been collected in the last two centuries and, in most cases, have caught the attention of taxonomists, who formally described several as new taxa. Therefore, taxonomic entities based on them have been validly published. In southern South America, among the ten taxonomic entities in the A. lateralis complex, five are natural hybrids and at least three possess legitimate names ( A. × coloratus , A. × lindmanii , and A. × subtilior ). Based on morphometric analyses and previous studies we propose that other two natural hybrids deserve taxonomic names. These entities are Andropogon × velutinus ( A . bicornis × A . glaziovii , = Andropogon sp 1 according to Zanin, 2001) and Andropogon × catarinensis ( A . bicornis × A . arenarius ). Taxonomic treatments of A . × velutinus and A . × catarinensis are presented.