抄録
There has been ongoing controversy over the taxonomy of Pleurochaete in North America. Some authors have recognized two species (P. luteola and P. squarrosa), whereas others have argued that these intergrade and should be treated as one species. Our examination of variation in the acknowledged key character, extent of the hyaline basal cells up the leaf margin, revealed a clear separation of New World plants into two groups. Geographical and ecological differences parallel the morphological variation, and extent of the hyaline margin appears to be a stable character that does not consistently vary with plant size, leaf length, or stressful environments as proposed by some authors. Evidence from other studies employing chloroplast and nuclear genomic markers lends support to the recognition of two distinct lineages in the New World. Moreover, these studies indicate that New World populations of “P. squarrosa” are not conspecific with Old World P. squarrosa, as many authors have assumed. Naming of the New World populations of “P. squarrosa” should await a thorough study that simultaneously analyzes both morphological and genetic variation.
