Print PageAn organism’s elemental ratios reflect underlying biochemical allocations that are produced to meet particular biological functions (e.g. growth & development). Despite the striking similarity in the elements involved in basic life processes, there is significant variation in the elemental stoichiometry of organisms that relates not only to structural features (e.g. size) but also to biological macromolecules (e.g. RNA, DNA). The growth rate hypothesis (GRH) proposes that major variation in the elemental stoichiometry of living things reflects the elevated demands for phosphorus (P) rich rRNA needed for rapid growth. We tested this hypothesis in natural populations of free living soil nematodes, S. lindsayae and P. murrayi from P-rich and poor environments. We quantified the level of rRNA transcription, rDNA copy numbers, body P-content and nematode growth parameters.
Results/Conclusions
Our results reveal very strong coupling of soil P-content with rRNA transcription, rDNA copy number and total body P-content (P < 0.05). Contrary to the GRH, body P-content was inversely correlated with nematode body size, indicating the possibility that adaptations to specific habitats, environmental conditions and life history traits may be more important determinants of body size. We show that elemental stoichiometry influences adaptive responses in gene expression and genome evolution, and illustrate how elemental stoichiometry can integrate multiple levels of ecological and evolutionary organization such as trophic interactions and nutrient cycling.
