Investigating the effects of nitrogen deposition and substrates on the microbiome and mycobiome of the millipede Cherokia georgiana georgiana (Diplopoda: Polydesmida)

Abstract

Millipedes are ubiquitous soil invertebrates that play major roles in physical and chemical processes in soil. Despite their importance to soil ecology and their presumed interactions with soil microorganisms, little is known about how millipedes influence and are influenced by soil microbes. Furthermore, it is not fully understood how these millipede-microbe interactions are influenced by available soil nitrogen, which is predicted to increase over the foreseeable future with increased anthropogenic production. Here, using the millipede Cherokia georgiana georgiana as a model and using a manipulative mesocosm and metabarcoding approach, we examine (1) the impacts of millipedes on soil microbial communities (fungi and bacteria) with varying nitrogen addition levels, and (2) the temporal impacts of nitrogen on millipede fecal communities (fungi and bacteria). This research demonstrates that millipede presence strongly alters soil communities and that alterations in nitrogen levels do not impact millipede gut communities. This work also provides the first evidence suggesting that millipede gut communities are predominantly derived from soils rather than leaf litter, though both contribute to gut composition. This work advances our current poor understanding of millipede-soil interactions and provides a framework for further investigations to disentangle the interactive effects of substrate, nitrogen, and time to better understand ecological impacts of these interactions.