Body stoichiometry of heterotrophs: Assessing drivers of interspecific variations in elemental composition

Aim The aim was to document how body stoichiometry of heterotrophs varies globally and to assess phylogenetic, trophic, habitat and body mass drivers of this interspecific variation in elemental composition, focusing on carbon (C), nitrogen (N) and phosphorus (P). Location World-wide. Time period 1930-2019. Major taxa studied Amphibians, fishes (Actinopterygii), invertebrates, mammals, microbes and sauropsids (birds and reptiles). Methods We compiled from the scientific literature a global database of body elemental composition of heterotrophs in marine, freshwater and terrestrial realms. We used model selection and ANCOVAs to investigate the proportion of variance in elemental composition explained by taxonomic groups, diet, habitat and body mass. We assessed the phylogenetic signal in body stoichiometry using Blomberg's K and Pagel's lambda statistics. We assessed the phylogenetic structure of interspecific variation in body stoichiometry using mixed models, with nested taxonomic levels as random factors. We finally assessed the covariations in elemental composition. Results Our database gathered 31,371 observations on 1,512 species. Body elemental composition was widely variable among species, with the four assessed drivers contributing significantly to this variation. Taxonomic group was the strongest contributor to interspecific variance for the stoichiometric traits studied, followed by habitat, diet and body mass. More precisely, C, N and P contents and C:N ratio were generally structured among classes, whereas the largest variations in C:P and N:P ratios were among families. This resulted in a significant but relatively modest phylogenetic signal. Finally, we found significant covariation among the three body elemental contents, resulting in taxonomic group-specific C:N:P spectra. Main conclusions Our global synthesis of body stoichiometry of heterotrophs revealed a strong interspecific variability that was only modestly explained by the species attributes investigated (body mass, habitat and diet). It also revealed that this taxonomically structured residual variation in body stoichiometry seemed to be constrained along taxonomic group-specific elemental spectra.

Automated summary

The study aimed to document global variations in body stoichiometry of heterotrophs and assess the drivers of this variation, focusing on carbon, nitrogen, and phosphorus. The research compiled a global database from scientific literature on body elemental composition, finding that the variations were significantly influenced by taxonomic groups, habitat, diet, and body mass. The results showed significant interspecific variability, with taxonomic group being the strongest contributor to the differences observed.