Similarity matrices of metagenomes. Squares along the diagonal represent the number of clusters where a sample occurs. Grayscale squares below the diagonal represent the occurrence profile coefficients rAB between two samples with a darker color indicating a greater similarity. Cells above the diagonal show the unique and overlapping clusters, explained in (c). Hierarchical clustering of samples based on the matrix is shown with vertical gridlines indicating the value of the coefficient where two nodes are merged. Matrices are made for GOS ORF clusters (a) and BIOME ORF clusters (b) with significant a factor f = 2 at 0.95 confidence level. The BIOME samples are grouped by biome type, such as Coral-M, which stands for coral microbiomes sample.