Fig. 2
Natural variations in stable isotope ratios (litter-normalized Δ13C and Δ15N values) of Protura as compared to other invertebrates. Each point represents mean stable isotope ratios of individual species in local communities; ellipses represent 95% confidence ranges. Note: the stable isotope niche of Protura resembles that of mycorrhizal fungi and differs from that of saprotrophic fungi (a) as well as the majority of other soil invertebrates (b). Data on saprotrophic fungi are based on fungal sporocarps from coniferous forests [56], data on invertebrates are based on soil animals from beech and coniferous forests [46]