Fig. 1

Laboratory setup. In the scheme each unique sequence has a different colour, and the different tags are represented by the differences in the continuity of the blue lines at the ends of the sequence. a DNA is extracted and the targeted barcode is amplified from each sample. More than one amplification reaction is performed, each PCR replicate with different tag combinations. Afterwards, double-tagged amplicon products can be pooled and constructed into a sequencing library that is subsequently amplified prior to sequencing. b Erroneous sequences are filtered based on (1) identification of unused tag combinations (which may be due to tag jumping), (2) chimeric sequences identification with clustering algorithms, and (3) the sequence copy number and reproducibility across the PCR replicates