A biosystematic study of the genus Eriochloa (Poaceae: Paniceae) in North America

Abstract

A biosystematics treatment was made of the grass genus Eriochloa in North America. This revision recognized the following 19 taxa: E. acuminate var acuminate, E. acuminate var. minor, E. aristata var. aristata, E. aristata var. boxiana, E. contracta, E. distachya, E. lemmonii, E. michauxii var. michauxii, E. michauxii var. simpsonii, E. nelsonii var nelsonii, E. nelsonii var. papillosa, E. pacifica, E. polystachya, E. procera, E. punctate, E. sericea, E. setosa var. setosa and E. setosa var. ekmanii. Two new status and new combinations were proposed (E. aristata var. boxiana and E. setosa var. ekmanii). One new combination E. acuminate var. minor was made, and a new variety (E. nelsonii var. papillosa) was described. Also, the species name E. gracilis was determined to be synonymous with E. acuminate which had nomenclatural priority. Anatomical and epidermal characteristics of the leaf-blade were described in detail, and they indicated that Eriochloa was a member of the Paniceae tribe. 13C ratios and leaf anatomy showed the genus utilizes the 4-carbon photosynthetic pathway. Neither leaf anatomy nor the leaf epidermis were of value in delineating taxa. Micromorpholigcal characteristics of the lemma and palea of the upper (perfect) floret were examined for numerous species using scanning electron microscopy. The lemma and palea were normally covered with numerous compound papillae in longitudinal rows, however, much variation was noted between taxa. Other surface features included bicelluar microhairs, macrohairs and prickles. Stomata were observed on the lawn of the lemma in two species. Spikelets from a specimen of E. contracta and E. michauxii var. michauxii were found with a well developed first glume adnate to the callus. This evidence clearly showed that the first glume in Eriochloa is much reduced and part of the callus. Chromosome counts of 2n=36 for E. contracta and E. acuminate var acuminate and 2n=54 for E. sericea confirm previous reports. The count of 2n=36 for E. acuminate var. minor was the first report for the taxa. All meiotic divisions observed were normal with no lagging or fragmented chromosomes...