Bryophyte C:N:P stoichiometry, biogeochemical niches and elementome plasticity driven by environment and coexistence.

Ecological stoichiometry and studies of biogeochemical niches have mainly focused on plankton and vascular plants, but the phenotypically closest modern relatives of early plants, bryophytes, have been largely neglected. We analysed C:N:P stoichiometries and elemental compositions (K, Na, Mg, Ca, S, Fe) of 35 widely distributed bryophyte species inhabiting springs. We estimated bryophyte C:N:P ratios and their biogeochemical niches, investigated how elementomes respond to the environment and determined whether they tend to diverge more for coexisting than non-coexisting individuals and species. The median C:N:P was 145:8:1, intermediate between Redfield's ratio for marine plankton and those for vascular plants. Biogeochemical niches were differentiated amongst species and were phylogenetically conserved. Differences in individual and species-specific elementomes increased with coexistence between species. Our results provide an evolutionary bridge between the ecological stoichiometries of algae and vascular plants and suggest that differences in elementomes could be used to understand community assemblages and functional diversity.