DNA metabarcoding marker choice skews perception of marine eukaryotic biodiversity

DNA metabarcoding is an increasingly popular technique to investigate biodiversity; however, many methodological unknowns remain, especially concerning the biases resulting from marker choice. Regions of the cytochrome c oxidase subunit I (COI) and 18S rDNA (18S) genes are commonly employed “universal” markers for eukaryotes, but the extent of taxonomic biases introduced by these markers and how such biases may impact metabarcoding performance is not well quantified. Here, focusing on macro-eukaryotes, we use standardized sampling from autonomous reef monitoring structures (ARMS) deployed in the world’s most biodiverse marine ecosystem, the Coral Triangle, to compare the performance of COI and 18S markers. We then compared metabarcoding data to image-based annotations of ARMS plates. Although both markers provided similar estimates of taxonomic richness and total sequence reads, marker choice skewed estimates of eukaryotic diversity. The COI marker recovered relative abundances of the d...