Data from: The evolution of energetic scaling across the vertebrate tree of life

Metabolism is the link between ecology and physiology—it dictates the flow
of energy through individuals and across trophic levels. Much of the
predictive power of metabolic theories of ecology derives from the scaling
relationship between organismal size and metabolic rate. There is growing
evidence that this scaling relationship is not universal, but we have
little knowledge of how it has evolved over macroevolutionary time. Here
we develop a novel phylogenetic comparative method to investigate how
often and in which clades the macroevolutionary dynamics of the metabolic
scaling have changed. We find strong evidence that the metabolic scaling
relationship has shifted multiple times across the vertebrate phylogeny.
However, shifts are rare and otherwise strongly constrained. Importantly,
both the estimated slope and intercept values vary widely across regimes,
with slopes that spanned across theoretically predicted values such as 2/3
or 3/4. We further tested whether traits such as ecto-/endothermy, genome
size, and quadratic curvature with body mass (i.e., energetic constraints
at extreme body sizes) could explain the observed pattern of shifts.
Though these factors help explain some of the variation in scaling
parameters, much of the remaining variation remains elusive. Our results
lay the groundwork for further exploration of the evolutionary and
ecological drivers of major transitions in metabolic strategy and for
harnessing this information to improve macroecological predictions.