The Evolution of Polyploid Genomes in Tragopogon (Asteraceae): Changes in Gene Content, Gene Expression, and Karyotypes

Tragopogon is a textbook model for studying allopolyploidy, with two recently (~80 years old; 40 generations in these biennials) and repeatedly formed natural allotetraploids, T. mirus and T. miscellus.  These species originated during the first half of the 20^th century from diploid parents (T. dubius and T. porrifolius and T. dubius and T. pratensis, respectively) that were introduced into North America from Europe.  These two species have each originated multiple times during the past 80 years in the narrow geographic region of eastern Washington and northern Idaho, USA.  Synthetic lines (S₀-S₅) of both allotetraploids have also been developed. In addition, the allotetraploid T. castellanus from Spain (0.5 - 1.5 million years old) provides an older polyploid for comparison. Moreover, ancient whole-genome duplication (WGD) also occurred deep in the history of Asteraceae. Tragopogon therefore presents research opportunities not available in other systems, providing the chance to investigate the patterns, tempo, mechanisms, and evolutionary forces driving post-WGD genome fractionation and diploidization.  We will provide both new data and an overview of the changes in gene expression, homeolog loss, and chromosomal changes that have occurred repeatedly in the unique evolutionary system provided by young polyploids in Tragopogon and extend these patterns deeper in time via analyses of T. castellanus and the early history of the Asteraceae.