Biology subjects

Romahn, J.

Publications and source records attributed to Romahn, J..

3 recordsLinked to original sources

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↗

bioRxiv2025

Multi-millennial genetic resilience of Baltic diatom populations disturbed in the past centuries

Little is known about the genetic diversity and stability of natural populations over millennial time scales, although the current biodiversity crisis calls for heightened understanding. Marine phytoplankton, the primary producers forming the basis of food webs in the oceans, play a pivotal role in maintaining marine ecosystems health and serve as indicators of environmental change. This study examines the genetic diversity and shifts in allelic composition in the diatom species Skeletonema marinoi over [~] 8000 years in the Baltic Sea by analyzing chloroplast and mitochondrial genomes. Ancient environmental DNA (aeDNA) from sediment cores demonstrates stability and resilience of genetic composition and diversity of this species across millennia in the context of major climate events. Accelerated change in allelic composition is observed from historical periods onwards, coinciding with times of intensifying human activity, like the Roman Empire, the Viking Age, and the Hanseatic Age, suggesting that anthropogenic stressors have profoundly impacted this species for the last two millennia. The data indicate a very high natural stability and resilience of the genomic composition of the species and underscore the importance of uncovering genomic disruptions caused by human impact on organisms, even those not directly exploited, to better predict and manage future biodiversity.

genomics↗

bioRxiv2023

No evidence for phylogenetic structure or environmental filtering of springtail microbiomes

Microorganisms play crucial roles in the lives of metazoans and can significantly impact host fitness. However, recent evidence suggests that many species may lack microorganisms that are positively associated with host fitness. Assessing the prevalence of host-specific microbiomes in animals has proven challenging due to limited studies in most higher taxa, with most investigations focusing on microbes in mammals, cephalopods, fish, and corals. This knowledge gap extends to springtails (Arthropoda: Collembola), which are widespread and abundant hexapods found in terrestrial and semi-aquatic habitats, contributing to important ecological functions. Here we investigated taxonomic bycatch in genome sequences generated from entire individuals of 70 springtail species. We aimed to understand whether microbial and other taxa associated with springtails are influenced by host phylogeny and environmental parameters. The analyses revealed high richness of bacteria and other taxa in the analyzed sequences, but detected no phylosymbiotic or environmental filtering signal in community composition. The findings suggest that springtails may be one of potentially many animal groups lacking distinct microbiomes. The study demonstrates how entire eukaryotic groups can be tested for phylosymbiotic patterns with taxonomic bycatch from genome sequences.

bioinformatics↗