Data from: Macroevolution of leaf defenses and secondary metabolites across the genus Helianthus

Leaf defenses are widely recognized as key adaptations and drivers of plant evolution. Across environmentally diverse habitats, the macroevolution of leaf defenses can be predicted by the univariate trade-off model, which predicts that defenses are functionally redundant and thus trade off, and the resource availability hypothesis, which predicts that defense investment is determined by inherent growth rate and that higher defense will evolve in lower resource environments. Here, we examined the evolution of leaf physical and chemical defenses and secondary metabolites in relation to environmental characteristics and leaf economic strategy across 28 species of Helianthus (the sunflowers). Using a phylogenetic comparative approach, we found few evolutionary trade-offs among defenses and no evidence for defense syndromes. We also found that leaf defenses are strongly related to leaf economic strategy, with higher defense in more resource-conservative species, although there is little support for the evolution of higher defense in low-resource habitats. A wide variety of physical and chemical defenses predict resistance to different insect herbivores, fungal pathogens, and a parasitic plant, suggesting that most sunflower defenses are not redundant in function and that wild Helianthus represents a rich source of variation for the improvement of crop sunflower.

叶片防御机制被广泛认定为植物演化的关键适应性性状与核心驱动因子。在环境异质性极强的各类生境中，叶片防御的宏演化模式可通过两个理论模型进行预测：其一为单变量权衡模型（univariate trade-off model），该模型假定防御性状存在功能冗余，进而产生演化权衡；其二为资源可用性假说（resource availability hypothesis），该假说提出防御投入由物种固有生长速率决定，且在低资源生境中会演化出更高水平的防御。本研究以28种向日葵属（Helianthus，即向日葵）植物为研究对象，探究了叶片物理防御、化学防御以及次生代谢物的演化规律，及其与环境特征和叶片经济策略（leaf economic strategy）的关联。本研究采用系统发育比较方法（phylogenetic comparative approach）开展分析，结果显示防御性状间几乎不存在演化权衡，也未发现防御综合征的相关证据。此外，本研究发现叶片防御水平与叶片经济策略显著相关：资源保守型更强的物种其防御水平更高，尽管几乎没有证据支持低资源生境中会演化出更强防御的理论预期。多种物理与化学防御机制可显著预测植物对不同植食性昆虫、真菌病原菌以及寄生植物的抗性，这表明多数向日葵防御性状并非功能冗余，且野生向日葵属植物是改良栽培向日葵的优质遗传变异资源库。