A recent treatment of the subtribe Muhlenbergiinae (Eragrostideae; Peterson 2000 in Grasses: Systematics and Evolution, Pp. 195-212.) suggested that Muhlenbergia (a large genus of about 153 species) shares a common ancestor with five smaller genera: Bealia, Blepharoneuron, Chaboissaea, Lycurus, and Pereilema. An ongoing phylogenetic study of this group based on internal transcribed spacer (ITS) region sequences (nrDNA) shows that these five genera are nested within a paraphyletic Muhlenbergia. In addition, four chloridoid genera that have been classified outside of the Muhlenbergiinae are also nested within Muhlenbergia: Aegopogon, Redfieldia, Schaffnerella, and Schedonnardus. Some well supported clades (i.e., with many base substitutions and high jackknife support) in the phylogeny correspond to existing formal and informal groups within Muhlenbergia. One clade consists entirely of species of Aegopogon, Muhlenbergia subg. Muhlenbergia, and Pereilema that exhibit PCK leaf anatomy. Another clade contains species that correspond to members of Muhlenbergia subg. Trichochloa (i.e., with sclerosed phloem in the primary vascular bundles and a crown of inflated cells just above the primary vascular bundles). Interestingly, ITS sequences within this clade have diverged little compared to other clades. Members of the Muhlenbergia montana complex, a group of caespitose perennials and annuals that usually have a 3-nerved and/or toothed upper glumes, form a clade. Another clade is composed entirely of annual species of Muhlenbergia, and Blepharoneuron tricholepis, a caespitose perennial. Although only 32 species of Muhlenbergia have been sampled at this writing, it is already clear that the ITS region will contribute much to our understanding of the diversification of this lineage.

Key words: Chloridoideae, Eragrostideae, molecular systematics, Muhlenbergia, Muhlenbergiinae, Poaceae