A biosystematic study of Clematis section Viorna subsection Viornae

A biosystematic study was conducted on Clematis subsection Viornae. Morphological, cytological, biochemical, ecological and distributional data were collected from herbarium, field and laboratory investigations. Three ordinations (Principle Components Analysis, Principle Coordinates Analysis and Non-metric Multidimensional Scaling Analysis) and a cladistic analysis (following procedures outlined by Nelson and Van Horn) were used to order taxa into phenetic and phylogenetic classifications. From these studies eight taxa are recognized: f. addisonii, f· glaucophylla, f· pitcheri var. pitcheri, f. pitcheri var. dictyota, C. reticulata, C. texensis, f· versicolor and C. viorna. Scanning electron microscopy (SEM) of pollen showed no interspecific differences. SEM was useful in illustrating the glaucous nature of four of the species (f. addisonii, C. glaucophylla, C. texensis, and C. versicolor) and the pubescence on the leaves and sterns of the non-glaucous species (f. pitcheri, f. reticulata, and f. viorna). It was also helpful in illustrating the "glandular" pubescence that had been attributed to C. gattingeri, a species described by Small. Field studies indicated that the taxa are generally separated by physiographic boundaries. Where different species do occur in the same physiographic province, they appear to prefer different habitats. In only two instances were two species found to occur in a true sympatric relationship.