A phylogeny and classification of the Muhlenbergiinae (Poaceae: Chloridoideae: Cynodonteae) based on plastid and nuclear DNA sequences

• Premise of the study : To understand the origins of C 4 grasslands, we must have a better interpretation of plant traits via phylogenetic reconstruction. Muhlenbergiinae, the largest subtribe of C 4 grasses in Mexico and the southwestern United States (with 176 species), is taxonomically poorly understood. • Methods : We conducted a phylogenetic analysis of 47 genera and 174 species using six plastid regions ( ndhA intron, ndhF, rps16‐trnK, rps16 intron, rps3 , and rpl32‐trnL ) and the nuclear ITS 1 and 2 (ribosomal internal transcribed spacer) regions to infer evolutionary relationships and revise the classification. • Key results : In our analyses, Muhlenbergia (ca. 153 species) is paraphyletic, with nine genera ( Aegopogon , Bealia , Blepharoneuron , Chaboissaea , Lycurus , Muhlenbergia , Pereilema , Redfieldia , Schaffnerella , and Schedonnardus ) found nested within. We recognized the following five well‐supported monophyletic lineages within Muhlenbergia : subg. Muhlenbergia , with species that have phosphoenolpyruvate carboxykinase‐like leaf anatomy and long, scaly rhizomes; subg. Trichochloa with long‐lived species that are relatively tall (up to 3 m); subg. Clomena with 3‐nerved upper glumes; sect. Pseudosporobolus species with narrow panicles and plumbeous spikelets; and sect. Bealia species with lemmas with hairy margins and midveins. • Conclusions: We propose expanding the circumscription of Muhlenbergia to include the other nine genera in this subtribe and make the following new combinations: Muhlenbergia subg. Bealia , M. diandra , M. geminiflora , M. paniculata , M. phleoides , M . subg. Pseudosporobolus (also lectotipified), M. solisii , M. tricholepis . We also propose several new names: M. ammophila , M. columbi , M. plumosa . Our phylograms suggest that Muhlenbergia originated in North America because the sister ( Sohnsia filifolia and Scleropogoninae) is composed of predominantly North American species.