An analysis of morphological variation in Senecio cymbalaria (Asteraceae)

Senecio cymbalaria Pursh is an arctic-alpine perennial that exhibits a broad range of morphological variation and occurs in four disjunct regions within North America. In this study, a morphological analysis of herbarium material is undertaken to determine whether the observed morphological variation is primarily attributable to morphological discontinuities among geographically isolated groups. Eighty individuals representing the total geographic range of the species were scored for 24 morphological characters and the data matrix subjected to principal components and cluster analyses. Individuals from the southern Rocky Mountains, previously recognized as Senecio conterminus, are separated from the remainder of S. cymbalaria in both analyses. Our results support recognition of two species, S. conterminus and S. cymbalaria. Although populations from the Gaspé and from Newfoundland form somewhat distinct clusters, neither can clearly be distinguished from populations of S. cymbalaria from Alaska, the Yukon, and Northwest Territories. Chromosome counts of 2n = 138 were obtained from two individuals from the Gaspé peninsula. Key words: biogeography, phenetics, Gulf of St. Lawrence, Senecio, disjunction, chromosome numbers.