XVI International Botanical Congess

The Tragopogon polyploid complex, in eastern Washington, has served as a model for investigations of many facets of polyploidy. Early work showed that, through hybridization, three introduced diploid Tragopogon species produced two tetraploid derivatives, T. mirus and T. miscellus. Work using morphology, DNA, allozymes, cytology, and flavonoid chemistry established that T. mirus had arisen at least five times and T. miscellus at least twice. RAPD markers have now been used to show that the independent origins of the tetraploids are numerous and widespread. Each tetraploid population had a unique RAPD marker profile, suggesting for each an origin independent of other populations in the region. In the Tragopogon genus in North America, each tetraploid species is spreading primarily through repeated polyploidization events. Such a pattern of repeated formation in polyploid species may increase the adaptive potential of newly formed polyploids.