Ongoing speciation within the diatom Fragilariopsis kerguelensis in the Southern Ocean?

While the identification of microbial eukaryotes using metabarcoding tools is now widespread, additional data are needed to confirm molecular observations, to mark the difference between species and population variants, and to better understand the biogeography of microbial eukaryotes. In this issue of Molecular Ecology, Postel et al not only use three molecular approaches to identify subgroups of Fragilariopsis kerguelensis but also use morphology and physiology to better understand the relationship between the three genotypes. They revealed that (a) the three genotypes of the diatom F. kerguelensis show negligible gene flux; (b) two of the genotypes are geographically isolated with different physiology but still able to crossbreed; and (c) the remaining genotype is omnipresent but reproductively isolated.