A biosystematic study of the Muhlenbergia repens Complex (Poaceae)

Abstract

A biosystematic treatment was made of the Muhlenbergia repens complex. Materials for morphological, anatomical, embryological, and cytological studies were collected from throughout the geographic region of this complex. Based on these studies six species are recognized: M. fastigiata, M. plumbea, M. repens, M. richardsonis, M. utilis, and M. villiflora. One new combination was made: M. villosa was submerged as a variety of M. villiflora. New biological descriptions are given for each of the recognized taxa. Floret vestiture was examined on each of the taxa by means of scanning electron microscopy. These investigations showed that, of the species traditionally referred to as "glabrous," three of the species examined were completely glabrous, with no vestiture of any kind, and two of the species had spikelets with minute or sparse pubescence on both lemma and palea. One species had florets with long villous macrohairs as previously described. This species and those with minute or sparse pubescence also have numerous papillae associated with the hairs. There is some evidence that the papillae represent non-functional or reduced macrohairs. A morphological examination was made on 117 populations of the complex. Phenetic and basic biostatistical techniques were used to delineate and define taxa. Principal components analysis, correlation and distance phenograms, and multivariate analysis were used to show spacial relationships among population clusters. Correlation coefficients, means, ranges, standard deviations, nested analysis of variance, and discriminant analysis were used to compare and define species. On the basis of these results, six species were defined. Detailed quantitative descriptions are given for leaf epidermal and internal anatomical characters. Characters of the abaxial epidermis and leaf transverse section were used to differentiate among the taxa. Differences between the varieties of M. villiflora were evident when leaves were viewed in transverse section. Leaf anatomical characters within the complex were typical of the Chloridoid-Eragrostoid type, this having been correlated with the C4 photosynthetic pathway, and specifically the NAD-me subtype. An indication was also found that rows of short cells on the epidermis of the leaf are only present if associated with sclerenchyma below the epidermal layer...