Dissertation Research: The Phylogeny and Biogeography of Linum (flax)

本研究的重点是亚麻属（Linum）的进化历史（系统发育）。除了具有重要经济价值的栽培亚麻外，世界上还有近200种亚麻分布在温带和亚热带地区。虽然这些物种中大约有一半局限于欧亚大陆，但黄花亚麻的一个谱系分布在整个欧洲、非洲南部和美洲。通过DNA序列分析，将确定140种Linum的进化关系，这些Linum代表了在这些地区定居和多样化的谱系。不同大陆物种之间的关系模式将被用来评估历史事件的重要性，如大陆漂移、迁徙和远距离分散在Linum的进化史上。系统发育也将检验一种假设，即向自相容交配系统的过渡在黄花亚麻向南部非洲和美洲殖民的能力中发挥了作用，而基本上自不相容的蓝花亚麻基本上仍然局限于欧亚大陆。作为纤维和亚麻籽油的来源，亚麻已经被种植了数千年。亚麻属植物的系统发育将为今后的作物改良和系统地从亚麻属植物中寻找其他有用化合物提供指导。最后，这项工作将提供生命之树部分的结构和历史的解决方案，增加我们对地球当前生物多样性起源的理解，以及北美植物群与南美、非洲和欧亚大陆植物群的关系。

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.