Fine-tuning biodiversity assessments: A framework to pair eDNA metabarcoding and morphological approaches
1. Accurate quantification of biodiversity can be demanding and expensive. Although environmental DNA (eDNA) metabarcoding can facilitate biodiversity assessments through non-invasive, cost-efficient, and rapid surveys, the approach struggles to outperform traditional morphological approaches in providing reliable quantitative estimates for surveyed species (e.g., abundance and biomass). ; 2. We present an integrated methodology for improving biodiversity surveys that pairs eDNA metabarcoding with morphological data, following a series of taxonomic and geographic filters. We demonstrate its power by applying it to a new spatiotemporal dataset generated on an Iberian-wide distributed aquatic mesocosm infrastructure that spans a wide biogeographic gradient. ; 3. By building upon the strengths that these two approaches offer, our framework improved taxonomic resolution for 30% of the taxa and enabled species' traits (e.g., body-size) and abundance to be assigned to 85% of the taxa in hybrid datasets. ; 4. These results indicate that eDNA-based assessments can complement, but not always replace, conventional approaches. Integrating conventional and modern eDNA metabarcoding approaches, already available in the ecologist's toolbox, will greatly enhance biodiversity assessments. ; This work was supported by the Portuguese Science and Technology Foundation (FCT) through the scientific projects TrophicResponses - Trophic responses to macroecological gradients (PTDC/BIA-BIC/0352/2014), and StateShifts - Predicting state shifts in energetic food webs under climate change (PTDC/AAG-MAA/3764/2014). This work was also funded by FEDER funds through the COMPETE 2020 Programme and National Funds through FCT under the project number POCI-01-0145-FEDER-007688 and PTDC/CTA-AMB/30793/2017 (AdaptAlentejo – Predicting ecosystem-level responses to climate change). The Iberian Pond network has received funding from the European Union's Horizon 2020 research and innovation programme under grant Nos 731065 (AQUACOSM) and 871081 (AQUACOSM-plus). CLP acknowledges support by the Portuguese Science and Technology Foundation (FCT) through PhD studentship (SFRH/BD/102020/2014). ; We acknowledge support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI). ; Peer reviewed