| A study of Boutelouinae (Gramineae: Chloridoideae) based on macromorphology, lemma micromorphology, and leaf blade transverse anatomy has yielded new insights into phylogenetic relationships. The subtribe is constituted of the genera Aegopogon (4 spp.), Bouteloua (24), Buchloe (1), Buchlomimus (1), Cathestecum (6, incl. 2 undescribed), Chondrosum (17), Cyclostachya (1), Griffithsochloa (1), Hilaria (12, incl. 2 undescribed), Melanocenchris (3), Neobouteloua (1), Opizia (2), Pentarrhaphis (3), Pringleochloa (1), Schaffnerella (1), and Soderstromia (1). The center of diversity is Mexico, with 14 genera, 66 species, and 26 of 27 varieties. Using a scanning electron microscope, considerable variation in the lemma abaxial surface was found. Much of this variation is believed to be of systematic utility. A notable discovery was the presence of short cells with relatively thin outer walls that collapse upon desiccation; these are uncharacterized in the literature. Much meaningful variation was also found in leaf blade structure, especially involving the arrangement of vascular bundles, features of the bundle outer sheath, and distribution of sclerenchyma. All data considered, Bouteloua and Chondrosum probably do not represent distinct, monophyletic assemblages: Bouteloua aristidoides, B. annua, C. eriopodum, and C. eriostachyum are likely most closely related to one another than to other species. The proper inclusion of B. juncea in the B. curtipendula complex is doubtful. Melanocenchris and Schaffnerella gracilis differ significantly from all other taxa and from one another and their affinities are uncertain. Dicliny appears to have evolved independently on at least two occasions. |
