Tracing Molecular Patterns of Adaptation in Arctic Brassicaceae: Evolutionary repeatability and adaptations to extreme abiotic stress

Abstract

A central objective of evolutionary biology is to understand how organisms adapt to novel environments, and to what degree this process follows repeatable patterns. This thesis explores how three Arctic plant species evolved to live in some of the coldest biomes on Earth, and how they developed similar adaptations to extreme light and temperature conditions. It consists of three complementary studies, whereof the first compares patterns of molecular evolution, the second examines how Arctic plants respond to cold, and the third presents the first genome assembly of an Arctic plant. The main finding is that the three species appear to have evolved similar suites of adaptations by modifying different components in similar stress response pathways, implying that there could be many genetic trajectories for adaptation to the Arctic environment. This lack of evolutionary repeatability differs from similar studies on other plant genera. The thesis represents the first molecular study of Arctic plant adaptations, and provides both a framework and the tools (in form of a genome assembly) for more in depth studies on the molecular ecology of Arctic plants.