ORIGINS OF THE NEW ALLOPOLYPLOID SPECIES SENECIO-CAMBRENSIS (ASTERACEAE) AND ITS RELATIONSHIP TO THE CANARY-ISLANDS ENDEMIC SENECIO-TENERIFFAE

The distribution of a 330 bp cpDNA insertion was reexamined in British material of Senecio cambrensis (2n = 6x = 60), its two putative paren tal taxa, S. squalidus (2n = 2x = 20) and S. vulgaris (2n = 4x = 40), and the closely related Canary Islands' endemic S. teneriffae (2n = 6x = 60). This formed part of a test of the hypothesis that the Welsh fo rm of S. cambrensis is derived from introduced S. teneriffae rather th an having originated in Wales val allopolyploidy as previously suppose d. It was established that the 330 bp insertion was carried by all pla nts of Welsh S. cambrensis and also S. teneriffae, but was absent from the cpDNA of Edinburgh S. cambrensis and all plants of British S. squ alidus and S. vulgaris var. vulgaris surveyed. However, two of 19 indi viduals tested of S. vulgaris var. hibernicus also possessed the cpDNA insertion, indicating that it is present in British material of S. vu lgaris, although at low frequency. The close similarity between S. ten eriffae and S. cambrensis, especially the Welsh form of S. cambrensis, was confirmed by the results of a restriction analysis of rDNA, and a lso morphometric and crossing studies, However, isozyme analysis showe d that S. teneriffae is monomorphic for beta EST-3 and ACO-1 phenotype s that are not present in Welsh nd Edinburgh S. cambrensis, nor in S. squalidus and S. vulgaris material surveyed. It is concluded that S. t eneriffae and S. cambrensis are two closely related allohexaploid taxa that have very similar, but different origins. It is postulated that whereas S. cambrensis (in Wales and Edinburgh) is the allohexaploid of S. vulgaris and S. squalidus, S. teneriffae is possibly the allohexap loid of S. vulgaris and S. glaucus, the latter being a diploid species closely related to S. squalidus.