Phylogenetic structural equation modelling reveals no need for an 'origin' of the leaf economics spectrum

The leaf economics spectrum (LES) is a prominent ecophysiological paradigm that describes global variation in leaf physiology across plant ecological strategies using a handful of key traits. Nearly a decade ago, Shipley et al. (2006) used structural equation modelling to explore the causal functional relationships among LES traits that give rise to their strong global covariation. They concluded that an unmeasured trait drives LES covariation, sparking efforts to identify the latent physiological trait underlying the ‘origin’ of the LES. Here, we use newly developed phylogenetic structural equation modelling approaches to reassess these conclusions using both global LES data as well as data collected across scales in the genus Helianthus. For global LES data, accounting for phylogenetic non-independence indicates that no additional unmeasured traits are required to explain LES covariation. Across datasets in Helianthus, trait relationships are highly variable, indicating that global-sc...叶片经济谱（leaf economics spectrum, LES）是主流的生理生态学范式，它借助少量关键功能性状，刻画了全球尺度下不同植物生态策略对应的叶片生理特征变异格局。近十年前，Shipley等人（2006）借助结构方程模型（structural equation modelling）探究了驱动叶片经济谱性状间全球显著协同变异的因果功能关联。他们的研究指出，某一未被观测的性状主导了叶片经济谱的协同变异，这一结论引发了学界探寻叶片经济谱"起源"背后潜在生理性状的研究热潮。本研究依托新近开发的系统发育结构方程模型（phylogenetic structural equation modelling）方法，结合全球尺度的叶片经济谱数据与向日葵属（Helianthus）不同采样尺度下的观测数据，对上述结论进行重新评估。针对全球尺度的叶片经济谱数据，纳入系统发育非独立性校正后，研究结果表明无需额外引入未观测性状即可解释叶片经济谱的协同变异。而在向日葵属的各数据集当中，性状间的关联关系存在高度变异性，这表明全球尺度[原文截断]