Advances in the phylogeny of the South American cool-season grass genus Chascolytrum (Poaceae, Pooideae): a new infrageneric classification

Chascolytrum, as currently circumscribed, includes 22–23 South American species that were previously included in nine different genera (Chascolytrum, Briza, Poidium, Calotheca, Microbriza, Gymnachne, Rhombolytrum, Lombardochloa and Erianthecium). Due to the remarkable morphological diversity, the relationships in Chascolytrum s.l. have remained poorly understood, and no infrageneric classification could be proposed based on the latest molecular phylogenetic studies. In this study, we combined molecular (GBSSI, trnL-trnL-trnF and rps16 intron) and morphological characters to investigate the phylogenetic relationships in Chascolytrum s.l. Based on this, morphologically diagnosable clades were recognized as eight sections (Calotheca, Chascolytrum, Hildaea, Lombardochloa, Microbriza, Obovatae, Poidium and Tricholemma), of which three are new and three are monospecific. We describe each section and discuss the new infrageneric classification in comparison with the previous infrageneric classification proposed for the group under the genus Briza. A taxonomic key and images for most of the species in each section are provided. Last, the use of single-copy nuclear genes and morphological data for future phylogenetic reconstructions encompassing Chascolytrum is highlighted.