Molecular phylogenetics, lemma micromorphology, and leaf blade anatomy of Aristida (Gramineae: Aristidoideae) with emphasis on North America.

摘要

Aristida (ca. 300 species) is one of three genera in Aristidoideae (Gramineae) along with Sartidia (4) and Stipagrostis (50). The genus is distributed in the tropics and subtropics, growing mostly on grassy plains, arid lands, and open ground. Studies of this taxonomically difficult genus have relied primarily on morphology and anatomy. Taxonomic groupings have been based principally on inflorescence architecture and awn characters. Aristida and Stipagrostis carry out C4 photosynthesis (NADP-ME and NAD-ME, respectively), whereas Sartidia undergoes C3 photosynthesis. Leaf blade anatomy, lemma micromorphology, and DNA sequence data (nuclear and chloroplast) have increased our knowledge of this group. Aristida , Stipagrostis and Sartidia are monophyletic. Sartidia is basal and sister to Stipagrostis . Both genera are sister to Aristida. A. longifolia is basal and sister to the remaining Aristida species. Aristida sections are monophyletic. There is strong support for these relationships. Aristida longifolia is the first C3 species within the genus and the second event of C3 within the subfamily.