Evolution of metabolic scaling among the tetrapod: effect of phylogeny, the geologic time of class formation, and uniformity of species within a class

Abstract

The metabolic scaling in the animal has been discussed for over 90 years, but no consensus has been reached. Our analysis of 2126 species of vertebrates reveals a significant allometric exponent heterogeneity. We show that classes of terrestrial vertebrates exhibit the evolution of metabolic scaling. Both the allometric coefficient “a” and the allometric exponent “b” change naturally, but differently depending on the geological time of group formation. The allometric coefficient “a” shows the measure of the evolutionary development of systems that forms resting metabolism in animals. Endothermic classes, such as birds and mammals, have a metabolic rate that is in an order of magnitude higher than that in ectothermic classes, including amphibians and reptiles. In the terrestrial vertebrate phylogeny, we find that the metabolic scaling is characterized by 3 main allometric exponent values: b = 3/4 (mammals), b > 3/4 (ectotherms, such as amphibians and reptiles), and b < 3/4 (birds). The heterogeneity of the allometric exponent is a natural phenomenon associated with the general evolution of vertebrates. The scaling factor decreases depending on both the external design and the size (birds vs mammals) of the animal. The metabolic rate and uniformity of species within a class increase as the geological start date of formation of the class approaches the present time. The higher the mass‐specific standard metabolic rate in the class, the slower metabolic rate grows with increasing body size in this class. Our results lay the groundwork for further exploration of the evolutionary and ecological aspects of the development of metabolic scaling in animals.

Metabolic Scaling in Birds and Mammals: How Taxon Divergence Time, Phylogeny, and Metabolic Rate Affect the Relationship between Scaling Exponents and Intercepts

“…Different groups, data sets, standardizations, and analytical approaches have provided different answers [ 1 , 2 , 3 , 4 , 5 , 7 , 8 , 10 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ]. The association of scaling parameters with evolutionary age has been studied by Zotin et al [ 24 , 28 ], Atanasov and Dimitrov [ 29 ], Ueda et al [ 39 ], and Gavrilov et al [ 68 ] on animals of different classes. In this report, we have applied three different methods of determining the metabolic rate and two methods of determining the slope in six groups of endothermic animals only.…”

“…To establish a BMR dataset we combined the available databases of BMR of birds and mammals. We conducted a survey of the available databases of the basal metabolic rate (BMR) of birds [ 68 ]. We selected only data collected from adult, post-absorptive, resting individuals within their thermoneutral zones, because these criteria are required for metabolic rate measurements to be basal [ 80 ].…”

“…In attempts to estimate the varying slope of the metabolic scaling relationship in evolution, it has been suggested that the slope is either static across evolutionary time or changes at the major taxonomic groups [ 39 , 68 ]. Previous studies have examined the question by dividing a database into predefined taxonomic units and using them as independent replicates for testing the universality of scaling parameters.…”

“…Here, we focus only on two factors (of the many noted in the works of Glazier [ 2 , 3 , 24 , 32 ]) that have an explanation for the observed variation in both the intercept and the slope. First, we account for the geological time when the group evolved suggesting that younger groups would have higher metabolic demands, as shown by Zotin and colleagues [ 25 , 26 , 27 , 28 ], also [ 29 , 68 ] Atanasov and Dimitrov [ 29 ], and Gavrilov et al [ 68 ]. Second, we have linked BMR with the level of activity because BMR is a proxy for the minimum metabolic power, which is required for “idling” the machinery that provides for any activity [ 24 , 77 , 78 ].…”

“…We recently showed that classes of terrestrial vertebrates exhibit the evolution of metabolic scaling. Both the allometric coefficient “ a ” and the allometric exponent “ b ” change differently depending on the geological time of group formation [ 68 ]. We found that the allometric exponent b regularly decreases from ectotherms to endotherms, while a is growing.…”