Fig. 4

Species-level diversity of Pelagibacterales as resolved by mOTUs3. a The number of taxonomic units within the Pelagibacterales order varies depending on the clustering method used, which was based on using marker gene (MG) sequences (used by mOTUs), average nucleotide identity (ANI) of whole genomes, and full-length 16S rRNA gene sequences. b mOTU marker gene distances better capture whole-genome distances compared to full-length 16S, explaining the patterns observed in a. In particular, 16S rRNA gene sequence identity saturates while whole-genome similarity can be as low as 70–80%. c The different clustering approaches vary in their agreement with each other as determined by the V-measure, which captures both the completeness and homogeneity of the clusterings. The highest agreement was found between mOTUs and with whole genome clustering by ANI