Life stage and taxonomy the most important factors determining vertebrate stoichiometry: A meta-analysis

1. Whole-body elemental composition is a key trait for determining how
organisms influence their ecosystems. Using mass-balance, ecological
stoichiometry predicts that animals with higher concentrations of element
X will selectively retain more X and will recycle less X in their waste
than animals with lower X concentrations. These animals will also store
high quantities of X during their lives and after their deaths (prior to
full decomposition). 2. Vertebrates may uniquely impact nutrient cycling
because they store high quantities of phosphorus (P) in their bones.
However, vertebrates have diverse body forms and invest variably in bone.
Current analyses of vertebrate elemental content predominately evaluate
fishes, typically neglecting other vertebrates and leaving much of the
diversity unexplored. 3. We performed a systematic review and identified
179 measurements of whole-body percent phosphorus (%P), percent nitrogen
(%N), and N to P ratio (N:P) from 129 unique species of non-fish
vertebrates (amphibians: 39 species; reptiles: 19 species; birds: 27
species; mammals: 46 species) 4. We found that %P (mean: 1.94%; sd
(standard deviation) = 0.77) and N:P (mean: 12.52) varied with taxonomy
and life stage, while %N (mean: 10.51%; sd = 3.25) varied primarily with
taxonomy. Habitat, diet, and size had small and inconsistent effects in
different groups. 5. Our study highlights two research gaps. Life stage,
which is frequently neglected in stoichiometric studies, is an important
factor determining vertebrate %P. Furthermore, amphibians dominate our
dataset, while other vertebrate taxa are poorly represented in the current
literature. Further research into these neglected vertebrate taxa is
essential.