HERRERA-ARRIETA, YOLANDA* AND PAUL M. PETERSON. CIIDIR IPN Unidad Durango, Apdo. Postal 57, Durango, Dgo. 34000 Mexico and Department of Botany, National Museum of Natural History, Smithsonian Institution, Washington, DC 20560. - An anatomcial survey of Muhlenbergia (Poaceae: Muhlenbergiinae).
Muhlenbergia, the largest grass genus in Mexico (118 spp.), contains
160 species, primarily of New World origin (8 spp. in southern Asia).
There exists no modern subgeneric classification within the genus and
species relationships are not clear. Soderstrom (1967) last divided
the genus into two subgenera, Muhlenbergia and Podosemum, the latter
with two sections, Epicampes and Podosemum. An anatomical survey of
the leaf blade as viewed in transverse section has provided a unique
set of characters to test previous hypothesized relationships. Over
the last 13 years, fresh field collected leaf blades have been
obtained from North, Central, and South America, as well as China.
Leaf material was fixed in FAA, dehydrated using an ethanol series,
infiltrated with paraffin, and then sectioned using a standard rotary
microtome. Sections were stained with safranin/fast green or
toluidine blue. A cladistic analysis utilizing more than 40
anatomical characters was performed on all species of Muhlenbergia.
Four major anatomical groups appear to support the division of
subgenus Podosemum into two clades. A new subgeneric classification
will be presented.
Key words: anatomy, Chloridoideae, Eragrostideae, Muhlenbergia, Muhlenbergiinae, phylogeny, Poaceae