ISSR as a tool to support taxonomic decisions: a first approach for Chascolytrum species complexes (Poaceae)

Abstract

Chascolytrum Desv. is a South American grass genus, with extension up to Central America, which presents several taxonomic controversies concerning genera and species circumscriptions. Morphological studies were not able to provide robust elements for taxonomic decisions in some species complexes. It was the case of Chascolytrum subaristatum and morphological allies, and of Chascolytrum rufum plus the acceptance (or rejection) of two varieties. In order to provide additional elements for taxonomic decisions in these species complexes, it was performed a preliminary survey using Inter Simple Sequence Repeat (ISSR) markers. Nine primers were used to build similarity dendrograms, and 25 collections were included, analysed in two separated complexes. ISSR were able to separate the two varieties of Chascolytrum rufum, supporting their acceptance. Two species recently described could be clearly separated from their morphologically related taxa, but the species Briza erecta, Briza macrostachya and Chascolytrum subaristatum, as well as Briza subaristata var. interrupta, could not be separated, adding elements to the synonymization of these three taxa under Chascolytrum ubaristatum. The ISSR contributed to solving some controversies on genus Chascolytrum, but its use as an exclusive species-marker is limited in this genus due to high band polymorphism.