Taxonomy of the North and South American species of Hordeum section Hordeastrum

Abstract

The four species H. euclaston Steud., H. flexuosum Nees ex Steud., H. intercedens Nevski, and H. pusillum Nutt. have been regarded as conspecific by some authors, because of a lack of markers for distinguishing among the species. Bothmer and co-workers recently recognized the four species but were unable to demonstrate morphological discontinuities that could be used in keys to permit definite identification to species. This paper provides new evidence from lodicule and epiblast characters for existence of four species. A key based on the rachilla, lodicules, and epiblast is presented. Furthermore, carefully defined morphometric characters of the four species were analysed by various discriminant analyses techniques. These analyses confirm the recognition of four morphological species and enable identification by means of resulting discriminant functions in addition to and complementary to the key.