Spiders as natural DNA samplers recover arthropod community diversity and biotic interactions across space and time

Global arthropod decline demands effective biodiversity monitoring strategies. However, most current monitoring approaches do not provide an exhaustive picture of arthropod community structure. In particular, biotic interactions and temporal patterns of biodiversity change are still poorly understood. Here we explore the possibility of addressing these two shortfalls using spiders, one of the most important predators of terrestrial arthropods, as natural samplers for arthropod community DNA. We conducted several experiments comparing the recovered community composition between spider gut contents and traditional monitoring methods. Additionally, we used archived spiders from long-term collections to assess the preservation of prey DNA over time. Spiders proved to be highly efficient natural DNA samplers, with gut content metabarcoding revealing similar community composition and alpha- and beta-diversity like traditional methods. Unique arthropod taxa were detected by spider gut contents and traditional methods respectively, indicating that these two approaches can serve as valuable complements to each other. Well-preserved archived spiders effectively reconstructed historical diets up to 20 years back in time, showing that historical spider collections can act as time capsules of the wider diversity that occurred in the spider's habitat. Spiders as natural samplers overcome critical shortfalls in biodiversity monitoring and contribute to our future understanding of community assembly across space and time.