Multiple genetic trajectories to extreme abiotic stress adaptation in Arctic Brassicaceae

Extreme environments offer powerful opportunities to study how different organisms have adapted to similar selection pressures at the molecular level. The Arctic is one of the most hostile environments on Earth, and the few plant species inhabiting this region typically possess suites of similar morphological and physiological adaptations to extremes in light and temperature. Here we compare patterns of molecular evolution in three Brassicaceae species that have independently colonized the Arctic, and present some of the first genetic evidence for plant adaptations to the Arctic environment. By testing for positive selection and identifying convergent substitutions in orthologous gene alignments for a total of 15 Brassicaceae species, we find that positive selection has been acting on different genes, but similar functional pathways in the three Arctic lineages. The positively selected gene sets identified in the three Arctic species showed convergent functional profiles associated with...