Dausmann, K. H. | bioRxiv Science

bioRxiv2025

Diversity and Functional Roles of Carabid Beetles across Salinity Gradients in Marshlands

Marsh ecosystems represent ecotones of high ecological significance where terrestrial and aquatic systems converge, governed by strong gradients in salinity and flooding. These environments sustain specialised communities and perform vital ecosystem functions such as carbon sequestration or nutrient cycling. This study examined carabid beetle (Coleoptera: Carabidae) assemblages across freshwater and saltwater marshes along the Elbe estuary in northern Germany to assess how environmental conditions shape patterns of abundance, diversity, and functional traits. Over 17,000 individuals representing 84 species were collected between March and October 2024. Despite similar species richness between marsh types, community composition differed markedly (Bray-Curtis dissimilarity: 0.92), reflecting environmental filtering along the salinity gradient. Freshwater marshes exhibited greater overall functional richness, while saltwater marshes supported more functionally even and divergent trait distributions, indicating stronger niche specialization under saline stress. Seasonal activity was bimodal in both habitats but peaked earlier in freshwater sites. A generalized linear mixed model revealed significant positive relationships between carabid activity abundance and functional richness of both dispersal- and preference-based traits. These findings demonstrate that salinity and flooding regimes drive distinct taxonomic and functional assemblages, with trait diversity underpinning ecosystem resilience and functioning. The study establishes an ecological baseline for future monitoring of marshland biodiversity and highlights the necessity of conserving functionally diverse communities to maintain the ecological integrity of tidal and floodplain marshes under changing environmental conditions.

ecology↗

bioRxiv2024

Between a Warm Winter and a Cold Spell: Physiological Responses to Changing Winter Climate in Amphibians

Climate change is swiftly altering environmental winter conditions, leading to significant ecological impacts such as phenological shifts in many species. As a result, animals might face physiological mismatches due to longer or earlier activity periods and are at risk of being exposed to late spring freezes. Our study points for the first time to the complex physiological challenges that amphibians face as a result of changing thermal conditions due to winter climate change. We investigated the physiological responses to a period of warmer winter days and sudden spring freeze in the common toad (Bufo bufo) by acclimating them to 4{degrees}C or 8{degrees}C for 48 h or exposing them to 4{degrees}C or -2{degrees}C for 6 h, respectively. We assessed the daily energy demands, determined body condition and cold tolerance, explored the molecular responses to freezing through hepatic tissue transcriptome analysis, and measured blood glucose levels. Toads acclimated to higher temperatures showed a higher daily energy expenditure and a reduced cold tolerance suggesting faster depletion of energy stores and the loss of winter acclimation during warmer winters. Blood sugar levels were higher in frozen toads indicating the mobilization of cryoprotective glucose with freezing which was further supported by changed patterns in proteins related to glucose metabolism. Overall, our results emphasize that increased thermal variability incurs physiological costs that may reduce energy reserves and thus affect amphibian health and survival. This might pose a serious threat to breeding adults and may have subsequent effects at the population level.

ecology↗