The evolution of marine phytoplankton under extreme polar conditions

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Marine phytoplankton has a huge biodiversity and biomass, yet despite its biological importance, these species remain woefully understudied. We were the first to sequence the genome of a polar phytoplankton species, and what we discovered shocked the scientific community. Firstly, we found that the genome of this species is fundamentally different from the genomes of other "model" species. We detected an overwhelming signature of positive selection, and discovered that a large proportion of its genes is evolving by natural selection, rather than by genetic drift. This finding flies in the face of the most fundamental theory of evolution, Kimura's (1968) Neutral Theory. It thus appears that the theory developed based on studies of classical model species (e.g. Drosophila) might be inadequate to understand the evolution of marine phytoplankton. Secondly, we discovered that this marine phytoplankton species employs its genetic variation in a unique manner which offers a significant evolutionary advantage; it can express alternative sets of alleles depending on the environment the organism encounters (Mock et al. 2017. Nature 541, 536-540).