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

Abstract

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). 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. 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). 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. 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.

Ontogenetic variation in the ecological stoichiometry of 10 fish species during early development

“…However, in vertebrates, bone is often the dominant P pool. The meta-analysis by May and El-Sabaawi (2022) though they usually have higher growth rates than older individuals. Our results agree with this scenario.…”

“…Thus, body stoichiometry is a potentially useful functional trait in the quest to scale individual traits to ecosystem processes (Chacon-Labella et al, 2022). However, we still know little about how ontogenetic changes in body stoichiometry vary across species, especially in vertebrates during early development (May & El-Sabaawi, 2022).…”

“…However, it is now clear that animals are less homeostatic than initially believed. In particular, animals may show substantial changes in body concentrations and stoichiometry during ontogeny (González et al, 2018; Knapp et al, 2021; May & El‐Sabaawi, 2022; Pilati & Vanni, 2007). Ontogenetic changes may be especially pronounced in vertebrates because their bones, which are rich in P, develop rapidly during early life (May & El‐Sabaawi, 2022).…”

“…In particular, animals may show substantial changes in body concentrations and stoichiometry during ontogeny (González et al, 2018; Knapp et al, 2021; May & El‐Sabaawi, 2022; Pilati & Vanni, 2007). Ontogenetic changes may be especially pronounced in vertebrates because their bones, which are rich in P, develop rapidly during early life (May & El‐Sabaawi, 2022). In adult vertebrates, bone is often the largest pool of body P (Hendrixson et al, 2007), but bones are not well developed in newborns.…”

“…Vertebrates show fairly consistent ontogenetic changes in body stoichiometry (May & El‐Sabaawi, 2022). In particular, body P concentration of young fish and amphibians is similar to that of invertebrates (~1% of dry mass) but increases greatly with development, reaching 2%–4% (or even higher in some very bony fish; El‐Sabaawi et al, 2016; Vanni et al, 2002).…”