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 are 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.新陈代谢是联结生态学与生理学的核心纽带——它支配着个体内部乃至跨营养级（trophic levels）的能量流动。生态学代谢理论的诸多预测效力，均源自生物体体型与代谢率之间的缩放关系（scaling relationship）。越来越多的研究证据表明，该缩放关系并非普适恒定，但学界对其在宏演化时间尺度上的演化轨迹却知之甚少。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演化动力学在多少次演化事件中、以及在哪些演化支（clades）中发生了改变。我们发现了强有力的证据，证明脊椎动物系统发育树中，代谢缩放关系已多次发生演化偏移；不过这类偏移整体较为罕见，且在其余情况下受到强烈约束。值得注意的是，不同演化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典型取值，如2/3或3/4。我们进一步检验了诸如外温/内温生理类型、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，能否解释观测到的演化偏移模式。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尚未得到合理解释。本研究结果为进一步探索代谢策略重大转变的演化与生态驱动因子，以及利用该信息优化宏观生态预测模型奠定了坚实基础。