The evolutionary consequences of polyploidy can best be studied in polyploids of known parentage and recent formation. Three diploid species of Tragopogon (T. dubius, T. pratensis, and T. porrifolius) were introduced into North America from their native ranges in Eurasia early in the 20th century. In Washington and Idaho these aliens hybridized and ultimately formed two new allotetraploids, T. miscellus (parents = T. dubius and T. pratensis) and T. mirus (parents = T. dubius and T. porrifolius). These new polyploids, which have never formed in Eurasia, were discovered in 1949 and are less than 80 years old. Tragopogon therefore affords a unique opportunity to examine the consequences of recent polyploidization in natural populations. A suite of molecular markers has documented that these two polyploids have formed repeatedly from different parental populations. Analyses of the rDNA cistron indicate that the polyploids retain contributions from both parental diploids; however, concerted evolution appears to be in progress, largely homogenizing the rDNAs. In both polyploid species, this concerted evolution has occurred in the direction of the maternal parent. Cytogenetic studies employing in situ hybridization (ISH) methods have made it possible to distinguish each of the six chromosome pairs in each parental diploid species. Based on the distribution of these cytogenetic markers, major chromosomal rearrangements have apparently not occurred in the newly formed polyploids. Application of AFLP cDNA display indicates that polyploid individuals express genes of one or the other parent, or of both parents, or exhibit novel gene expression. Importantly, individuals of T. miscellus from populations of independent origin differ in gene expression. Anatomical and physiological comparisons of diploids and polyploids demonstrate that T. miscellus populations of reciprocal parentage differ in cell size and measures of photosynthetic capacity.

Key words: evolutionary consequences, gene expression, genome evolution, polyploidy, Tragopogon