The focus of this research is on the evolutionary history (phylogeny) of the flax genus, Linum. In addition to the economically important cultivated flax, Linum usitatissimum, there are nearly 200 flax species distributed throughout the temperate and subtropical regions of the world. While approximately half of these species are confined to Eurasia, a lineage of yellow-flowered flaxes is distributed throughout Europe, Southern Africa, and the Americas. The evolutionary relationships among 140 species of Linum, representing the lineages that have colonized and diversified in these areas, will be determined through analysis of DNA sequences. The pattern of relationships among species on different continents will be used to assess the importance of historical events such as continental drift, migration, and long-distance dispersal in the evolutionary history of Linum. The phylogeny will also test the hypothesis that the transition to self-compatible mating systems had a role in the ability of the yellow-flowered flaxes to colonize Southern Africa and the Americas, while the largely self-incomapatible blue-flowered species essentially remain confined to Eurasia. Flax has been cultivated for thousands of years as a source of fibers and linseed oil. A phylogeny of Linum will provide a guide for future crop improvement and for the systematic search for additional useful compounds from flaxes. Finally, this work will provide a resolution of the structure and history of portion of the Tree of Life, increasing our understanding of the origins of the Earth's current biodiversity and the relationship of the North American flora to those of South America, Africa, and Eurasia.
