DNA metabarcoding of spiders, insects, and springtails for exploring potential linkage between above- and below-ground food webs

Background: Understanding feedback between above-and below-ground processes of biological communities is a key to the effective management of natural and agricultural ecosystems. However, as above-and below-ground food webs are often studied separately, our knowledge of material flow and community dynamics in terrestrial ecosystems remains limited. Results: We developed a high-throughput sequencing method for examining how spiders link above-and below-ground food webs as generalist predators. To overcome problems related to DNA-barcoding-based analyses of arthropod-arthropod interactions, we designed spider-specific blocking primers and Hexapoda-specific primers for the selective PCR amplification of Hexapoda prey sequences from spider samples. By applying the new DNA metabarcoding framework to spider samples collected in a temperate secondary forest in Japan, we explored the structure of a food web involving 15 spider species and various taxonomic groups of Hexapoda prey. These results support the hypothesis that multiple spider species in a community can prey on both above-and below-ground prey species, potentially coupling above-and below-ground food-web dynamics. Conclusions: The PCR primers and metabarcoding pipeline described in this study are expected to accelerate nuclear marker-based analyses of food webs, illuminating poorly understood trophic interactions in ecosystems.