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.

新陈代谢（Metabolism）是联结生态学与生理学的核心纽带，其主导着个体内部以及跨营养级（trophic levels）的能量流动过程。生态代谢理论的多数预测能力，均源自生物体体型与代谢速率之间的代谢缩放关系（scaling relationship）。越来越多的研究证据表明，该缩放关系并非普适性存在，但学界对其在宏进化（macroevolutionary）时间尺度上的演化历程仍知之甚少。本研究开发了一种全新的系统发育比较方法（phylogenetic comparative method），用以探究代谢缩放的宏进化动态在脊椎动物支系（clades）中的发生频率与具体分布。研究结果提供了强有力的证据，表明代谢缩放关系在脊椎动物系统发育（vertebrate phylogeny）历史中已发生过多次转变。但此类转变事件整体较为稀少，且在多数情况下受到极强的约束。值得注意的是，不同代谢模式下的估计斜率与截距值均存在显著差异，其斜率覆盖了理论预测的2/3、3/4等经典数值。本研究进一步检验了变温性/恒温性（ecto-/endothermy）、基因组大小以及与体重相关的二次曲率（即极端体型下的能量约束）等性状，能否解释已观测到的代谢缩放关系转变模式。尽管上述因素能够部分解释缩放参数的变异，但仍有大量剩余变异无法得到合理解释。本研究结果为进一步探究代谢策略重大转变的进化与生态驱动因子，以及利用该类信息优化宏生态预测（macroecological predictions）模型奠定了重要基础。