“…We could advocate achieving this via comparative genomics, but this usually necessitates hundreds to thousands of closely related genomes (for review see Read and Massey, 2014;Chen and Shapiro, 2015), as well as a refined phenotypic characterization of the sequenced strains. Alternatively, one could search in situ data for genes or substitutions related to a particular niche or environmental parameter (see e.g., Kent et al, 2016;Grébert et al, 2018;Ahlgren et al, 2019;Garcia et al, 2020). Given the wealth of marine metagenomes that are becoming available for a large variety of environmental niches, such an approach should be particularly powerful to unveil niche adaptation processes in the forthcoming years.…”