Stable isotope composition of mycophagous collembolans versus mycotrophic plants: Do soil invertebrates feed on mycorrhizal fungi?

Ectomycorrhizal fungi constitute a large proportion of the belowground microbial biomass and contribute significantly to nutrient cycling, but their role in soil food webs remains poorly known. In this study, we compared the delta C-13 and delta N-15 values of collembolans and mycoheterotrophic plants. Stable isotope composition of collembolans was very similar to those of mycotrophic plants associated with saprotrophic fungi. In contrast, mycotrophic plants associated with mycorrhizal fungi were enriched in N-15 relative to collembolans by at least 5 parts per thousand. Our data suggest that soil collembolans do not use mycorrhizal fungi as the main food source, and support an emerging view that extramatrical mycorrhizal mycelium can be retained in the soil to serve as a progenitor of stabilized soil organic matter. (C) 2015 Elsevier Ltd. All rights reserved.