Molecular and morphological evidence for the origin of Solidago albopilosa (Asteraceae), a rare endemic of Kentucky

Solidago albopilosa Braun is a rare tetraploid goldenrod endemic to sandstone rockhouses in eastern Kentucky. Previous studies have indicated similarity in morphology between S. albopilosa and S. flexicaulis and possible hybridization between the species. The purpose of this study was to examine the nature of the relationship between S. flexicaulis and S. albopilosa. Solidago flexicaulis is reported to hybridize with only one other goldenrod, S. caesia. Cytology, enzyme electrophoresis, and RAPD markers were used to examine the hypothesis that S. albopilosa is an autotetraploid derivative of S. flexicaulis or alternatively is an allotetraploid resulting from hybridization between S. flexicaulis and S. caesia. In addition, artificially produced F-1 hybrids produced from crosses between S. caesia and S. flexicaulis were compared morphologically with individuals of S. albopilosa. There was no evidence that either of these species has a recent close relationship with S. albopilosa. However, morphological and isozyme comparisons indicate that S. albopilosa is most similar to S. flexicaulis. The similarity between these species may indicate an ancient autopolyploid origin for S. albopilosa from S. flexicaulis.