Data from: Quantitative DNA metabarcoding: improved estimates of species proportional biomass using correction factors derived from control material

DNA metabarcoding is a powerful new tool allowing characterization of
species assemblages using high-throughput amplicon sequencing. The utility
of DNA metabarcoding for quantifying relative species abundances is
currently limited by both biological and technical biases which influence
sequence read counts. We tested the idea of sequencing 50/50 mixtures of
target species and a control species in order to generate relative
correction factors (RCFs) that account for multiple sources of bias and
are applicable to field studies. RCFs will be most effective if they are
not affected by input mass ratio or co-occurring species. In a model
experiment involving three target fish species and a fixed control, we
found RCFs did vary with input ratio but in a consistent fashion, and that
50/50 RCFs applied to DNA sequence counts from various mixtures of the
target species still greatly improved relative abundance estimates (e.g.
average per species error of 19 ± 8% for uncorrected vs. 3 ± 1% for
corrected estimates). To demonstrate the use of correction factors in a
field setting, we calculated 50/50 RCFs for 18 harbour seal (Phoca
vitulina) prey species (RCFs ranging from 0.68 to 3.68). Applying these
corrections to field-collected seal scats affected species percentages
from individual samples (Δ 6.7 ± 6.6%) more than population-level species
estimates (Δ 1.7 ± 1.2%). Our results indicate that the 50/50 RCF approach
is an effective tool for evaluating and correcting biases in DNA
metabarcoding studies. The decision to apply correction factors will be
influenced by the feasibility of creating tissue mixtures for the target
species, and the level of accuracy needed to meet research objectives.