Morphometric analysis of Schizachyrium beckii and allies (Poaceae - Andropogoneae) reveals two new species of Schizachyrium from South America

PEICHOTO, M. C.; WELKER, C.; VIVIANA GRISELDA SOLIS NEFFA

New Orleans

Congreso; Botany 2013; 2013

Botanical Society of America

Schizachyrium Nees belongs to the tribe Andropogoneae (Poaceae - Panicoideae) and includes ca. 60 species distributed in tropical and subtropical regions of the world, especially America and Africa. It is represented in America by ca. 30 species, 19 of which occurring in South America, from Colombia to Chile, Argentina and Uruguay. These taxa were divided into two groups based on morphological studies. One of them includes taxa with highly branched inflorescences and slender rachis internodes, flexuous at maturity, while the other group is characterized by sparsely branched inflorescences and thick rachis internodes, straight at maturity. Although the genus has been revised recently to South America, a group of specimens from Brazil and Paraguay with straight rachis internodes but usually highly branched inflorescences was found. They are morphologically similar to Schizachyrium beckii. Some of them also exhibit great morphological similarity with the type material of Andropogon luxurians, considered to date a synonymous of S. sanguineum. The aim of this paper is to assess the morphological variation of these specimens to clarify their taxonomic identity. To accomplish this purpose, 37 exomorphological traits (15 qualitative and 22 quantitative characters) were analyzed using multivariate methods (cluster and principal coordinate analyses). The analysis included 27 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 different 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, and the other restrict to Brazil. Moreover, Andropogon luxurians proved as a distinct taxon from Schizachyrium sanguineum, being proposed the new combination of the name for the genus Schizachyrium. Description and illustrations of the two new species are presented, as well as a key to separate them from other morphologically related species.