ELECTROPHORETIC RELATIONSHIPS AND PHYLOGENY OF NORDIC POLYPLOIDS IN DRABA (BRASSICACEAE)

104 populations of 15 Nordic species (2x-16x) of the taxonomically complex genus Draba were investigated using enzyme electrophoresis. The polyploids were genetic alloploids showing high levels of fixed heterozygosity and electrophoretic variation; the diploids were homozygous and genetically depauperate. Thus, the data suggest that alloploidy in arctic-alpine Draba serves as an escape from genetic depauperation caused by inbreeding at the diploid level. Although some populations probably have local alloploid origins, electrophoretic data indicate that several polyploids have migrated repeatedly into the Nordic area. Draba crassifolia (2n = 40) is probably octoploid based on x = 5. A hypothesis on the evolutionary history of the polyploids based on x = 8 is presented. Diploids contributing to numerous polyploid genomes and multiple origins of polyploids have seriously blurred taxonomic relationships. Relationships inferred from genetic data do not always correspond to those based on morphology; two morphologically very similar polyploids, D. alpina and D. oxycarpa, were, for example, genetically distant and probably represent independent lineages.