Koschorreck, J. | bioRxiv Science

bioRxiv2025

Two decades of compositional restructuring of soil biodiversity in Germany despite stable a- and b-diversity indices

Soil ecosystems host some of the most taxonomically and functionally diverse biological communities on Earth, yet long-term trends in their biodiversity remain poorly understood. Here, we analysed soil biodiversity dynamics over 20 years with samples archived in the German Environmental Specimen Bank. We assessed temporal and spatial patterns in -diversity and {beta}-diversity with shotgun metagenomics across bacteria, fungi, and metazoa. We found no statistically significant temporal trends in -diversity for any group. Total {beta}-diversity also appeared temporally stable. However, decomposing {beta}-diversity into its balanced variation and abundance gradients revealed taxon-specific compositional restructuring. Bacterial and fungal communities showed signs of compositional homogenisation, while metazoan communities remained more stable. Spatial structuring was pronounced across all groups. Land use emerged as a key spatial predictor of community composition for bacteria and fungi, and geographic locality for metazoans. Our findings show that apparent stability in standard biodiversity indices may mask significant underlying community change. This highlights the need for integrative, taxonomically inclusive approaches to biodiversity monitoring. The combination of environmental specimen banking with metagenomic sequencing offers a powerful framework for uncovering hidden biodiversity trends in soil ecosystems and identifying the drivers of ecological reorganisation under global change.

ecology↗

bioRxiv2021

Beyond fish eDNA metabarcoding: Field replicates disproportionately improve the detection of stream associated vertebrate species

Fast, reliable, and comprehensive biodiversity monitoring data are needed for environmental decision making and management. Recent work on fish environmental DNA (eDNA) metabarcoding shows that aquatic diversity can be captured fast, reliably, and non-invasively at moderate costs. Because water in a catchment flows to the lowest point in the landscape, often a stream, it can often collect traces of terrestrial species via surface or subsurface runoff along its way or when specimens come into direct contact with water (e.g., for drinking purposes). Thus, fish eDNA metabarcoding data can provide information on fish but also on other vertebrate species that live in riparian habitats. This additional data may offer a much more comprehensive approach for assessing vertebrate diversity at no additional costs. Studies on how the sampling strategy affects species detection especially of stream-associated communities, however, are scarce. We therefore performed an analysis on the effects of biological replication on both fish as well as (semi-)terrestrial species detection. Along a 2 km stretch of the river Mulde (Germany), we collected 18 1-L water samples and analyzed the relation of detected species richness and quantity of biological replicates taken. We detected 58 vertebrate species, of which 25 were fish and lamprey, 18 mammals, and 15 birds, which account for 50%, 24%, and 7% of all native species to the German federal state of Saxony-Anhalt. However, while increasing the number of biological replicates resulted in only 25% more detected fish and lamprey species, mammal, and bird species richness increased disproportionately by 69% and 84%, respectively. Contrary, PCR replicates showed little stochasticity. We thus emphasize to increase the number of biological replicates when the aim is to improve general species detections. This holds especially true, when the focus is on rare aquatic taxa or on (semi-)terrestrial species, the so-called bycatch. As a clear advantage, this information can be obtained without any additional sampling or laboratory effort when the sampling strategy is chosen carefully. With the increased use of eDNA metabarcoding as part of national fish bioassessment and monitoring programs, the complimentary information provided on bycatch can be used for biodiversity monitoring and conservation on a much broader scale.

molecular biology↗