DSSS - From DNA to ecosystems – the promise of metabarcoding biological archives for biodiversity monitoring

Alarming and dramatic biodiversity declines have been reported across the globe. However, comparatively few standardized historical time series datasets are available to identify the causes and patterns of the observed declines. Novel sources of data for analyzing biodiversity change across time and space are thus urgently needed. By metabarcoding highly standardized biota samples from a long-term pollution monitoring archive in Germany, we here analyze community diversity for several ten thousand species across the tree of life from terrestrial marine and limnic environments across four decades. The archived samples—tree leaves, marine macroalgae, and marine and limnic mussels—represent natural community environmental DNA (eDNA) samplers. They preserve a taxonomically diverse imprint of their associated biodiversity at the time of collection. Tree leaves and macroalgae preserve eDNA traces of taxa, which interacted with the plant’s tissue, for example from bite marks or leaf mines. The mussel’s digestive tract contains an imprint of the eDNA, which they filtered out of the water column. By metabarcoding these eDNA sampler organisms, we reconstruct patterns of community diversity over four decades. Our results show no patterns of universal biodiversity decline at individual sites. Instead, a gradual taxonomic turnover emerges as universal pattern of temporal biodiversity change in Germany’s terrestrial and aquatic arthropod communities. Through the immigration of novel widespread taxa and the loss of many site-specific ones, this turnover results in biotic homogenization throughout ecosystems. Germany’s ecosystems hence harbor less, but more widespread species.