Reinstatement and expansion of the genus Anatherum (Andropogoneae, Panicoideae, Poaceae)

The genus Andropogon sensu lato is known to be polyphyletic. Accordingly, we here adjust part of the classification of the genus to reflect its evolutionary history and morphological diversity. A plastome phylogeny including 20 new plastome sequences confirms a well-supported clade of species broadly corresponding to Andropogon section Leptopogon. Morphological diversity was assessed across Andropogon sensu lato using specimens held at the K, MO, and A/GH herbaria, GrassBase, and photographs of spikelet pairs, with an emphasis on identifying members of this clade and their distinguishing features. The genus Anatherum is here reestablished, expanded to incorporate 45 of the 131 of Andropogon sensu lato species worldwide, and described and illustrated. Five species names in Anatherum are reinstated and new combinations are made for 40 species and one subspecies. Anatherum is most common and diverse in the Americas but also commonly found across Africa. Few species occur in Europe or Asia. Anatherum inflorescences generally have 2 branches, linear and slender internodes and pedicels with long trichomes, small elliptic to lanceolate spikelets, and flat to concave 2-keeled lower glumes with no intercarinal veins visible. Generic circumscription in this group is complicated by its polyploid history and limited understanding of the relationship between genomic composition and key morphological characters. Five species of doubtful generic affiliation are listed for future analysis.