Metabolic rate is often cited as the fundamental rate which determines the rate of all biological processes by shaping energetic availability for the various physiological, behavioral, and life-history traits that contribute to performance. It has therefore been suggested that metabolic rate drives the widely observed covariance among these different levels of phenotypic traits. However, much of the work on this topic has relied on pairwise correlational analysis on a handful of traits at a time, leaving an important gap in our understanding regarding the functional links that shape this phenotypic covariance, often referred to as pace of life. Using honeybees as a model, we measured a large number of behavioral, life-history, and physiological traits in individual bees and used a path analysis to demonstrate that variation in metabolic rate plays a fundamental proximate role in driving the covariance among these traits. We combined this with a factor analysis in a structural equation model framework to characterize the overall phenotypic covariance or the pace-of-life axis in honeybees. We discuss the importance of these findings in the context of how interindividual variation in terms of slow–fast phenotypes may drive the phenotype of a group and the functional role metabolic rate might play in shaping division of labor and social evolution. The study provides empirical support for the theoretical idea that metabolic rate acts as a proximate driver of phenotypic covariance among several physiological, behavioral, and life-history traits at the individual level and that behavior acts as a mediator for how metabolic rate affects life history. In addition, using honeybees as an experimental model for this study establishes a framework for asking questions regarding how these individual-level phenotypic covariance patterns lead to observed phenotypic covariance patterns at the colony level, an idea which has functional consequences for division of labor and social evolution. The results of this study therefore contribute toward a better understanding of the rules of life that shape processes across different levels of biological organization. Our use of different structural equation modeling approaches for inferring heuristics and proximate causal relationships among multiple phenotypic traits also informs future research efforts on this topic.

中文翻译：

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代谢率塑造蜜蜂生理、行为和生活史特征之间的表型协方差

代谢率通常被认为是决定所有生物过程速率的基本速率，它通过塑造有助于表现的各种生理、行为和生活史特征的能量可用性。因此，有人提出代谢率驱动了这些不同水平的表型性状之间广泛观察到的协方差。然而，关于这个主题的大部分工作都依赖于一次对少数几个特征的成对相关分析，这在我们对形成这种表型协方差（通常称为生活节奏）的功能联系的理解方面留下了重要的空白。以蜜蜂为模型，我们测量了大量的行为、生活史、和单个蜜蜂的生理特征，并使用路径分析证明代谢率的变化在推动这些特征之间的协方差方面起着基本的近似作用。我们将其与结构方程模型框架中的因子分析相结合，以表征蜜蜂的整体表型协方差或生活节奏轴。我们在慢-快表型方面的个体间变异如何驱动一个群体的表型以及代谢率在塑造劳动分工和社会进化中可能发挥的功能作用的背景下讨论了这些发现的重要性。该研究为理论观点提供了经验支持，即代谢率是几种生理、行为、和生活史特征在个人层面上，这种行为作为代谢率如何影响生活史的中介。此外，使用蜜蜂作为本研究的实验模型建立了一个框架，用于询问有关这些个体水平的表型协方差模式如何导致在群体水平上观察到的表型协方差模式的问题，这一想法对劳动分工和社会进化。因此，这项研究的结果有助于更好地理解影响不同生物组织层次的过程的生命规则。我们使用不同的结构方程建模方法来推断多个表型特征之间的启发式和近似因果关系，也为该主题的未来研究工作提供了信息。