Data from: Evolution of the leaf economics spectrum in herbs: evidence from environmental divergences in leaf physiology across Helianthus (Asteraceae)

The leaf economics spectrum (LES) describes a major axis of plant functional trait variation worldwide, defining suites of leaf traits aligned with resource-acquisitive to resource-conservative ecological strategies. The LES has been interpreted to arise from leaf-level trade-offs among ecophysiological traits common to all plants. However, it has been suggested that the defining leaf-level trade-offs of the LES may not hold within specific functional groups (e.g., herbs) nor within many groups of closely-related species, which challenges the usefulness of the LES paradigm across evolutionary scales. Here we examine the evolution of the LES across 28 species of the diverse herbaceous genus Helianthus (the sunflowers), which occupies a wide range of habitats and climate variation across North America. Using a phylogenetic comparative approach, we find repeated evolution of more resource-acquisitive LES strategies in cooler, drier, and more fertile environments. We also find macroevolutionary correlations among LES traits that recapitulate aspects of the global LES, but with one major difference: leaf mass per area is uncorrelated with leaf lifespan. This indicates that whole-plant processes likely drive variation in leaf lifespan across Helianthus, rather than leaf-level trade-offs. These results suggest that LES patterns do not reflect universal physiological trade-offs at small evolutionary scales.

叶片经济谱（leaf economics spectrum, LES）描述了全球范围内植物功能性状变异的核心轴，定义了与资源获取型至资源保守型生态策略相对应的成套叶片性状组合。传统观点认为，LES源于所有植物共有的生理生态性状间的叶片水平权衡。然而，有研究指出，LES的核心叶片水平权衡关系在特定功能群（如草本植物）以及多数近缘物种类群中并不成立，这对LES范式在跨进化尺度上的应用价值提出了挑战。本研究针对分布于北美多样生境与气候梯度下的28种多样性草本属植物向日葵属（Helianthus），探究了LES的进化模式。通过系统发育比较分析方法，本研究发现，在凉爽、干旱且高肥力的生境中，资源获取型更强的LES策略多次独立进化。同时，本研究发现LES性状间的宏观进化相关性大体复刻了全球LES的特征，但存在一处显著差异：单位叶面积干质量与叶寿命无相关性。这表明，向日葵属内叶寿命的变异主要由整株植物过程驱动，而非叶片水平的权衡关系。上述结果提示，LES模式并非反映小进化尺度下普适性的生理权衡关系。