MOLECULAR SYSTEMATICS OF THE GENUS SENECIO-L .1. HYBRIDIZATION IN A BRITISH POLYPLOID COMPLEX

A survey of chloroplast DNA and nuclear ribosomal DNA variation was conducted in the allohexaploid Senecio cambrensis, the putative introgressant S. vulgaris var. hibernicus and their parental taxa: S. vulgaris var. vulgaris and S. squalidus. Ribosomal DNA allowed the differentiation of the two parental taxa and supported the hybrid origin of S. cambrensis at three of the four sites sampled; at the fourth site, in Edinburgh, non-additive rDNA phenotypes were found. No evidence, for or against the introgressive origin of var. hibernicus was found. Chloroplast DNA analysis provided independent evidence for the dual origin of S. cambrensis in Wales and Scotland, although the two parental taxa could not be distinguished.