Living organisms display an extraordinary amount of phenotypic variation driven and constrained by environmental and evolutionary pressures. The relevant aspect of that phenotypic variance are functional traits and specific trait combinations may reveal ecological strategies and represent suites of covarying traits that evolved in response to selection pressures. Global-scale analyses of functional trait variation and the shape of the multidimensional niche occupied by living organisms help to identify general characteristics of organismal form, function, and strategy. The elemental content of living organisms (carbon, nitrogen and phosphorus) are the building blocks of life and they represent key functional traits because they demonstrate a strong influence over organismal form and function. Using a global database of elemental traits of animals, a multidimensional niche space was quantified to answer the following questions (i) What is the overall size, shape, and boundaries of the functional trait space of animals? (ii) Is the observed trait space of animals constrained compared the potential niche space? (iii) Are there stoichiometric niche differences between invertebrates and vertebrates occupying different habitats?
Results/Conclusions
The observed multidimensional trait space of animals (vertebrates and invertebrates pooled together) was much smaller than the potential niche space, which suggests the occurrence of trait correlations. Carbon and nitrogen were responsible for 50.51% of the variance of the the trait space, while phosphorus was responsible for 33.88%. The trait space of vertebrates and invertebrates revealed they differed in their use of the main chemical elements. The vertebrate niche shape was influenced more evenly by the three elements, while the invertebrate niche showed much less skew in phosphorus content. This is likely due to the fact that vertebrates sequester phosphorus in their bones. Further study will seek to explore whether the structural demands of terrestrial versus aquatic habitats cause a variance in animals’ use of C,N, and P.