Chromosomal Evolution, Genetic Diversity, and Speciation Mechanisms in Polyploid Tragopogon (Asteraceae)

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Polyploidy, or whole genome duplication, is a major force in flowering plant evolution, with many flowering plant species having originated through the combined processes of hybridization and polyploidy. Chromosomal changes may generate genetic diversity via loss and duplication of genes in polyploids and may promote speciation, but the extent of chromosomal evolution in young, naturally occurring polyploid plants is unknown. Molecular cytogenetic methods will be used to investigate chromosomal and genomic changes in Tragopogon mirus and T. miscellus of the sunflower family. These species formed recently (in the past 80 years) and repeatedly through hybridization of different populations of the parental species. Furthermore, synthetic lines of both polyploids have been produced in the lab. Tragopogon therefore provides a unique opportunity to compare chromosomal variation in young natural and synthetic polyploid plants. This project will address the extent of chromosomal variation in new polyploids, whether or not certain "rules" govern the types of changes that occur, and the effect of this variation in natural populations. Polyploidy is common in flowering plants (a group of 300,000 or more species). Furthermore, all of the world's major crops and most serious weeds are polyploid. Therefore, characterizing the processes that take place shortly after polyploid formation is crucial for understanding the genomes of most plant species, and thus for our ability to conserve plant biodiversity and sustainably benefit from it. In conjunction with DNA sequence analyses, this project will provide new insight into the process of polyploidization at the chromosomal, genomic, and genetic levels.