Warming alters cascading effects of a dominant arthropod predator on fungal community composition in the Arctic

• Published in: mBio
• Main Authors: Koltz, Amanda M., Koyama, Akihiro, Wallenstein, Matthew
• Other Authors: Giovannoni, Stephen J., Weedon, James, National Science Foundation
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Society for Microbiology 2024
• Subjects: Arctic; Climate change; Tundra
• Online Access: http://dx.doi.org/10.1128/mbio.00590-24; https://journals.asm.org/doi/pdf/10.1128/mbio.00590-24

ABSTRACT Rapid climate change in the Arctic is altering microbial structure and function, with important consequences for the global ecosystem. Emerging evidence suggests organisms in higher trophic levels may also influence microbial communities, but whether warming alters these effects is unclear. Wolf spiders are dominant Arctic predators whose densities are expected to increase with warming. These predators have temperature-dependent effects on decomposition via their consumption of fungal-feeding detritivores, suggesting they may indirectly affect the microbial structure as well. To address this, we used a fully factorial mesocosm experiment to test the effects of wolf spider density and warming on litter microbial structure in Arctic tundra. We deployed replicate litter bags at the surface and belowground in the organic soil profile and analyzed the litter for bacterial and fungal community structure, mass loss, and nutrient characteristics after 2 and 14 months. We found there were significant interactive effects of wolf spider density and warming on fungal but not bacterial communities. Specifically, higher wolf spider densities caused greater fungal diversity under ambient temperature but lower fungal diversity under warming at the soil surface. We also observed interactive treatment effects on fungal composition belowground. Wolf spider density influenced surface bacterial composition, but the effects did not change with warming. These findings suggest a widespread predator can have indirect, cascading effects on litter microbes and that effects on fungi specifically shift under future expected levels of warming. Overall, our study highlights that trophic interactions may play important, albeit overlooked, roles in driving microbial responses to warming in Arctic terrestrial ecosystems. IMPORTANCE The Arctic contains nearly half of the global pool of soil organic carbon and is one of the fastest warming regions on the planet. Accelerated decomposition of soil organic carbon due to warming could cause ...