Upscaling biodiversity monitoring: Metabarcoding estimates 31,846 insect species from Malaise traps across Germany

Abstract

Mitigating ongoing losses of insects and their key functions (e.g. pollination) requires tracking large-scale and long-term community changes. However, doing so has been hindered by the high diversity of insect species that requires prohibitively high investments of time, funding and taxonomic expertise when addressed with conventional tools. Here, we show that these concerns can be addressed through a comprehensive, scalable and cost-efficient DNA metabarcoding workflow. We use 1815 samples from 75 Malaise traps across Germany from 2019 and 2020 to demonstrate how metabarcoding can be incorporated into large-scale insect monitoring networks for less than 50 € per sample, including supplies, labour and maintenance. We validated the detected species using two publicly available databases (GBOL and GBIF) and the judgement of taxonomic experts. With an average of 1.4 M sequence reads per sample we uncovered 10,803 validated insect species, of which 83.9% were represented by a single Operational Taxonomic Unit (OTU). We estimated another 21,043 plausible species, which we argue either lack a reference barcode or are undescribed. The total of 31,846 species is similar to the number of insect species known for Germany (~35,500). Because Malaise traps capture only a subset of insects, our approach identified many species likely unknown from Germany or new to science. Our reproducible workflow (~80% OTU-similarity among years) provides a blueprint for large-scale biodiversity monitoring of insects and other biodiversity components in near real time.

Keywords: DNA metabarcoding; Malaise trap; biodiversity monitoring; insect diversity.

FIGURE 1

(a) Location of the in total 75 Malaise traps across Germany, (b) Lateral view of a Malaise trap with collection bottle protected from sunlight at the upper left end and (c) Top view of a preserved Malaise trap sample spread in a white tray.

FIGURE 2

Top row: Rarefaction curves showing richness of insect OTUs and validated species richness that were either observed (solid lines) or estimated (dotted lines). Bottom row: Shared and unique absolute numbers and proportions of the insect OTUs (left circles) and validated insect species (right circles) collected in 2019 and 2020.

FIGURE 3

Top panels: Number of total insect OTUs, plausible and validated insect species per order identified in the present study compared to the total number of species reported from Germany or sampled in Germany and included in the BOLD database (data accessed on 14 April 2023). Bottom left panel: Percentage of OTUs assigned to species. Bottom right panel: Mean number of distinct OTUs assigned to a given plausible species.