Phenotypic variation of the introduced perennial Solidago gigantea in Europe

The exotic perennial Solidago gigantea belongs to the most widespread and abundant plant invaders in Europe, found throughout the range from northern Italy to southern Scandinavia. Morphological variation of this species in Europe was assessed by scoring plants from 22 populations along a north-south transect for quantitative and qualitative characters. All size related and floral characters varied significantly among populations. Size related characters exhibited large coefficients of variation and high intraclass correlations. Floral characters varied considerably less and showed rather narrow unimodal distributions. Pubescence of leaf main vein varied from glabrous to weakly pubescent. Leaf surfaces beneath as well as secondary veins were uniformly glabrous among the shoots. The first three principal components accounted for 56.5% of the variation and formed no separated clusters among the shoots sampled. Chromosome counts revealed only tetraploid cytotypes (2n=36). The low variation in taxonomic key characters and chromosome numbers suggest that the tetraploid cytotype of S.gigantea has became naturalized in Europe, probably the result of only few introductions of this species to Europe.