Fig. 3

Visual representation of read depths originating from hypothetical taxa x, y, and z present in a 1:2:1 ratio. The left distribution shows fragments resulting from reduced sequencing under size selection or PCR fragment length biases. The differences in relative abundance estimates produced using mean and median read depths is compared with the taxonomic ratio approach (FLTR) introduced here. The ratio table on the right displays the averaged pairwise read depth ratios calculated individually within each fragment length. Even assuming no bias within each fragment length, the mean and median read depth estimates produce relative abundances that don’t account for variance in the size distribution, which is often not normal or uniform