On the taxonomic position of Panicum aristellum (Poaceae: Panicoideae: Paniceae)

In a recent treatment, the genus Panicum was restricted to subgenus Panicum based on molecular, morphological, and anatomical data. Also, other species of Panicum were transferred to different genera of the Paniceae, such as Dichanthelium, Hymenachne, Phanopyrum, and Steinchisma, while the remaining American species of Panicum were temporarily placed as incertae sedis taxa. Therefore, these incertae sedis species are in need of a new taxonomic status within the tribe. In this study, the taxonomic position of Panicum aristellum, an endemic species of central and southeastern Brazil, is evaluated using morphological and anatomical characters, together with sequence data from ndhF a molecular marker from the chloroplast. The sequence of Panicum aristellum was analyzed together with other species of the subfamily Panicoideae. This species grouped with the genus Canastra in a well-supported clade. Several synapomorphies characterized the clade: caespitose plants, keeled sheaths, aristate spikelets, scabrous bracts, the number of nerves of the glumes and lower lemma, the presence of a lower palea and lower flower, a non-indurate upper anthecium, and a similar geographical distribution. In addition, both species are C-3 with non-Kranz anatomy. As a result, die new combination Canastra aristella is proposed and the species is compared to putatively related genera within the Paniceae.