The role of taxonomic expertise in interpretation of metabarcoding studies

The performance of DNA metabarcoding approaches for characterizing biodiversity can be influenced by multiple factors. Here we used morphological assessment of taxa in zooplankton samples to develop a large barcode database and to assess the congruence of taxonomic identification with metabarcoding under different conditions. We analyzed taxonomic assignment of metabarcoded samples using two genetic markers (COI, 18S V1-2), two types of clustering into molecular operational taxonomic units (OTUs, ZOTUs), and three methods for taxonomic assignment (RDP Classifier, BLASTn to GenBank, BLASTn to a local barcode database). The local database includes 1042 COI and 1108 18S (SSU) barcode sequences, and we added new high-quality sequences to GenBank for both markers, including 109 contributions at the species level. The number of phyla detected and the number of taxa identified to phylum varied between genetic marker and among the three methods used for taxonomic assignments. Blasting the metab...