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Jacobaea vulgaris subsp. vulgaris constitutes an intricate polyploid complex distributed in Europe. Four chromosome numbers have been reported in this species: 2n=20, 40, 80 and 32. Chromosome number 2n=20 reported from Bulgaria is due to misidentification with J. aquatica. We discovered new hexaploid (2n=6x=60) cytotype occuring within four sympatric populations of otherwise tetraploid and octoploid plants in the Czech Republic, Slovakia and Ukraine. The frequency of hexaploid individuals within 76 studied populations is very low (only 10 of 693 analysed plants), and hexaploids probably represent hybrids between tetraploid and octoploid plants. Multivariate morphometric analysis reveals partial separation of tetraploid and octoploid plants, whereas hexaploid individuals are similar to octoploids. Octoploids and hexaploids exhibit slightly longer ray florets, involucral bracts and tubular florets and more hairy outer achenes. Hexaploid plants display larger pollen grains and lower pollen fertility. |
