Limits to Evolutionary Adaptation of Phytoplankton in the Arctic Ocean

As single-celled microbes with large population sizes and high replication rates, phytoplankton species have considerable potential to adapt rapidly to changing environmental conditions. This can happen by (i) individual organisms adapting their phenotypes through epigenetic processes (i.e. phenotypic plasticity), (ii) by natural selection acting on individual genotypes, and by (iii) group selection (i.e. lineage and species-sorting). These three fundamental levels of selection result in changes in physiology, population genetic composition and community structure, respectively, which in turn can drive changes in both biogeochemical cycles and higher trophic levels. These adaptive changes already occur in the Arctic Ocean, yet existing climate models fail to capture these combined ecological and evolutionary adaptive responses. This proposal aims to address this fundamental gap in knowledge by studying adaptive evolution at the level of the genome, epigenome and transcriptome of a model species for polar diatoms, Fragilariopsis cylindrus, as well as 10 diatom species from the Arctic Ocean. We will thus address how environmental changes such as the loss of sea ice in the Arctic Ocean will impact the adaptive evolution and diversity of key primary producers with consequences for biogeochemical cycles in an ecosystem that is under extreme threat by global warming.