Data from: Trophic consistency of supraspecific taxa in belowground invertebrate communities: comparison across lineages and taxonomic ranks

1. Animals that have similar morphological traits are expected to share
similar ecological niches. This statement applies to individual animals
within a species and thus species often serve as the functional units in
ecological studies. Species are further grouped into higher-ranked
taxonomic units based on their morphological similarity and thus are also
expected to be ecologically similar. On the other hand, theory predicts
that strong competition between closely related species may result in
differentiation of ecological niches. Due to high diversity and limited
taxonomic expertise, soil food webs are often resolved using supraspecific
taxa such as families, orders or even classes as functional units. 2. Here
we tested the trophic differentiation and consistency of supraspecific
taxa across major lineages of temperate forest soil invertebrates:
Annelida, Chelicerata, Myriapoda, Crustacea and Hexapoda. Published data
on stable isotope compositions of carbon and nitrogen were used to infer
basal resources and trophic level, and explore the relationship between
taxonomic and trophic dissimilarity of local populations. 3. Genera and
families had normal and unimodal distributions of isotopic niches,
suggesting that supraspecific taxa are trophically consistent. The
isotopic niche of local populations varied considerably resulting in large
overlap of niches among species. Within the same genus, the effect of
species identity on stable isotope composition of populations was not
significant in 92% of cases. More than 50% of the variability in Δ15N
values (trophic level) across lineages was explained by classes and
orders, while the variability in Δ13C values (basal resources) was
explained mostly by families and genera. The variability in stable isotope
composition in Chelicerata and Hexapoda was explained by lower taxonomic
ranks than in Myriapoda. 4. We compiled a comprehensive list of mean Δ13С
and Δ15N values of invertebrate taxa from temperate forest soils allowing
to refine soil food-web models when measurements of trophic niches of
local populations are not feasible. Supraspecific taxa are meaningful as
trophic nodes in food-web studies, but the consistency varies among taxa
and the choice of taxonomiс resolution depends on the research question;
generally, identification of taxa should be more detailed in more diverse
taxonomic groups.