A taxonomic revision of Echinacea (Asteraceae: Heliantheae)

A morphometric analysis was conducted of Echinacea Moench (Asteraccae) to measure variation between native populations for taxonomic purposes. Data were collected from living and herbarium specimens, From a matrix of 321 specimens by 74 characters, a pair-wise distance matrix was computed using Gower's coefficient, Cluster strategies were explored from the distance matrix. MODECLUS clustering separated the data into two clusters,and a flexible agglomerative clustering method separated the data into the same two clusters, which were broken into four sub-clusters. Canonical discriminant analysis gave significant support for the two- and the four-cluster solutions Canonical discriminant analysis also showed support for eight smaller clusters identified using McGregor's 1968 classification, We recognize two subgenera and four species: Echinacea subg. Echinacea contains only E. purpurea; Echinacea subg. Pallida contains E atrorubens, E. laevigata, and E. pallida. The revised varieties are as follows: E atrorubens var. atrorubens, E. atrorubens var. neglecta, E, atrorubens var. paradoxa, E. pallida var. angustifolia, E. pallida var. pallida, E pallida var. sanguinea, E. pallida var. simulata, and E. pallida var. tennesseensis. A cladistic analysis was done on the four species. In the most parsimonious solution, E, purpurea was basally divergent to a clade of the other three species (70% bootstrap value), and all four were distinguishable by at least one apomorphy. A key to Echinacca taxa is provided, which should be valuable given the pharmaceutical and horticultural importance of Echinacea.