High dimensionality of stoichiometric niches in soil fauna.

The ecological niche is a fundamental concept to understand species' coexistence in natural communities. The recently developed framework of the multidimensional stoichiometric niche (MSN) characterizes species' niches using chemical elements in living organisms. Despite the fact that living organisms are composed of multiple elements, stoichiometric studies have so far mostly focused on carbon (C), nitrogen (N), and phosphorus (P), and therefore a quantitative analysis of the dimensionality of the MSN in living organisms is still lacking, particularly for animals. Here we quantified 10 elements composing the biomass of nine soil animal taxa (958 individuals) from three trophic groups. We found that all 10 elements exhibited large variation among taxa, which was partially explained by their phylogeny. Overlaps of MSNs among the nine soil animal taxa were relatively smaller based on 10 elements, compared with those based on only C, N, and P. Discriminant analysis using all 10 elements successfully differentiated among the nine taxa (accuracy: 90%), whereas that using only C, N, and P resulted in a lower accuracy (60%). Our findings provide new evidence for MSN differentiation in soil fauna and demonstrate the high dimensionality of organismal stoichiometric niches beyond C, N, and P.