Metabarcoding of PCR blank
A fragment of the mitochondrial cytochrome c oxidase subunit I (mtCOI) gene using primers mlCOIintF: 5' GGWACWGGWTGAACWGTWTAYCCYCC 3' and jgHCO2198: 5' 5' TANACYTCNGGRTGNCCRAARAAYCA 3' (~313 bp; (Leray et al. 2013; Geller et al. 2013) was amplified using polymerase chain reaction (PCR). PCR amplification was conducted in duplicate and products were pooled for library preparation. Pooled amplicons were purified using AMPure® XP beads (Beckman Coulter®), quantified using a Qubit® 1X dsDNA High Sensitivity Fluorescence kit (Thermofisher Scientific). Full methods description is reported at publication in Supplementary file S1.