Phylogeny of Muhlenbergia subg. Pseudosporobolus, including M. spatha (Poaceae, Chloridoideae, Cynodonteae, Muhlenbergiinae) now found in Zacatecas, Mexico.

Muhlenbergia spatha , previously known only from near the type locality in San Luis Potosí, is reported from two localities in Zacatecas, Mexico. Historically, botanists have overlooked this diminutive annual. To clarify affinities of M. spatha , we present a molecular phylogeny emphasising species in M. subg. Pseudosporobolus using sequence data from two plastid markers ( rpl32-trnL and rps16 intron) and nrDNA ITS. In addition, we include an updated description, illustration and discussion of the habitat of M. spatha .