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）刻画了全球范围内植物功能性状变异的核心维度，界定了一系列与资源获取型到资源保守型生态策略相匹配的叶片性状组合。此前学界普遍认为，叶片经济谱源于所有植物共有的生态生理性状间的叶片水平权衡关系。然而有研究指出，叶片经济谱所界定的叶片水平权衡关系，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，这对叶片经济谱范式在跨演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多样化草本属——向日葵属（Helianthus）的28个物种，探究了叶片经济谱的演化规律。通过系统发育比较方法（phylogenetic comparative approach），我们发现，在凉爽、干旱且肥力较高的生境中，资源获取型更强的叶片经济谱策略经历了多次独立演化。本研究还发现，叶片经济谱各性状间的宏观演化相关性呼应了全球尺度的叶片经济谱特征，但存在一处关键差异：比叶质量（leaf mass per area）与叶片寿命并无关联。这表明，向日葵属内叶片寿命的变异更可能由整株植物的生理过程驱动，而非叶片水平的权衡关系。上述结果表明，叶片经济谱的模式并不反映小演化尺度下普适性的生理权衡关系。