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

Abstract

Analysis of metabolic scaling in currently living endothermic animal species allowed us to show how the relationship between body mass and the basal metabolic rate (BMR) has evolved in the history of endothermic vertebrates. We compared six taxonomic groups according to their energetic characteristics and the time of evolutionary divergence. We transformed the slope of the regression lines to the common value and analyzed three criteria for comparing BMR of different taxa regardless of body size. Correlation between average field metabolic rate (FMR) of the group and its average BMR was shown. We evaluated the efficiency of self-maintenance in ordinary life (defined BMR/FMR) in six main groups of endotherms. Our study has shown that metabolic scaling in the main groups of endothermic animals correlates with their evolutionary age: the younger the group, the higher the metabolic rate, but the rate increases more slowly with increasing body weight. We found negative linear relationship for scaling exponents and the allometric coefficient in five groups of endotherms: in units of mL O2/h per g, in relative units of allometric coefficients, and also in level or scaling elevation. Mammals that diverged from the main vertebrate stem earlier have a higher “b” exponent than later divergent birds. A new approach using three criteria for comparing BMR of different taxa regardless of body mass will be useful for many biological size-scaling relationships that follow the power function.

Metabolic rate, sleep duration, and body temperature in evolution of mammals and birds: the influence of geological time of principal groups divergence

“…May we emphasise that the patterns of metabolic scaling found by us for endotherms ( Gavrilov et al 2022b and present study) regarding the change in indicators a and b depending on the geological time of the origin of the group are fully confirmed by the data on all vertebrates. The allometric coefficient a increases as the origin of the group approaches.…”

“…We combined data on ectotherms and endotherms using our data from previous works ( Gavrilov et al 2022a , b ) on reptiles and amphibians on scaling of metabolic rates and literature data ( White and Seymour 2003 ; White et al 2006 ) also as on the number of species in the taxon and its size range (Table 4 ).…”

“…Further, of the three models, the model with separate intercepts and fixed slope has the lowest BIC -1778.22. Further information can be found in Gavrilov et al (2022b) .…”

Mechanistic models project bird invasions with accuracy

“…Therefore, instead of simply collecting more biophysical trait data for more species, studies should focus on collecting those data that best enable the testing, development and refinement of predictive hypotheses about how biophysical functional traits are likely to vary across space, time and phylogeny. For example, empirical measurements of (basal) metabolic rates—which determine heat generating capacity—are currently available for only about 10% of the world’s bird species 62 . Although body-mass-based scaling laws 63 may serve as a first reasonable approximation, much uncertainty remains about the factors underlying inter- and intraspecific variation in metabolic rates (e.g., whether tropical birds are characterized by lower and less plastic metabolic rates compared to birds from temperate regions 64 ).…”

Host space, not energy or symbiont size, constrains feather mite abundance across passerine bird species

“… is the scaling exponent for host mass‐specific metabolic rate and equals to , where is the scaling exponent for whole‐organism metabolic rate to body size. is ∼3/4 across multicellular species (Hechinger, 2013), although it is estimated in 0.668 for the particular case of passerines (Gavrilov et al., 2022). Thus, , and .…”