Data from: Attracting mutualists and antagonists: plant trait variation explains the distribution of specialist floral herbivores and pollinators on crops and wild gourds

PREMISE OF THE STUDY:
Floral traits play important roles in pollinator attraction and defense against floral herbivory. However, plants may experience trade-offs between conspicuousness to pollinators and herbivore attraction. Comparative studies provide an excellent framework to examine the role of multiple traits shaping mutualist and antagonist interactions.
METHODS:
To assess whether putative defensive and attractive traits predict species interactions, we grew 20 different Cucurbitaceae species and varieties in the field to measure interactions with pollinators and herbivores and in the greenhouse to assess trait variation. Cucurbits are characterized by the production of cucurbitacins, bitter nonvolatile terpenoids that are effective against generalist herbivores but can attract specialist beetles. We determined whether plant traits such as cucurbitacins predict herbivore resistance and pollinator attraction using an information-theoretic approach.
KEY RESULTS:
Mutualists and floral antagonists were attracted to the same cucurbit varieties once they flowered. However, rather than cucurbitacin concentration, we found that the size of the flower and volatile emissions of floral sesquiterpenoids explained both pollinator and floral herbivore visitation preference across cucurbit taxa. This pattern held across cucurbit taxa and within the Cucurbita genus.
CONCLUSIONS:
Surprisingly, floral sesquiterpenoid volatiles, which are associated with direct defense, indirect defense, and attraction, rather than defense traits such as cucurbitacins, appeared to drive interactions with both pollinators and floral herbivores across cucurbit taxa. Identifying the relevant plant traits for attraction and deterrence is important in this economically valuable crop, particularly if pollinators and floral herbivores use the same plant traits as cues.

研究背景与前提：
花部性状（floral traits）在传粉者（pollinator）吸引与抵御花部植食为害中发挥关键作用。然而，植物往往面临对传粉者的显眼程度与吸引植食者之间的权衡效应。比较研究为解析多重性状在塑造互利共生与拮抗互作中的作用提供了极佳的研究框架。
研究方法：
为评估推定的防御与吸引性状能否预测物种互作模式，我们于田间种植了20个不同的葫芦科（Cucurbitaceae）物种与品种，以测定其与传粉者和植食者的互作关系；同时于温室中开展栽培实验以评估性状变异。葫芦科植物以合成葫芦素（cucurbitacins）为典型特征，这类苦味非挥发性萜类化合物可有效抵御广食性植食动物，但可能吸引专食性甲虫。我们采用信息论方法，解析葫芦素等植物性状能否预测植食动物抗性与传粉者吸引能力。
主要结果：
开花后，互利共生生物与花部拮抗生物均会被同一葫芦科品种所吸引。但研究发现，并非葫芦素浓度，而是花部大小与花部倍半萜类（sesquiterpenoids）挥发物，能够解释葫芦科各类群间传粉者与花部植食者的访花偏好差异。这一规律在葫芦科类群整体及南瓜属（Cucurbita）内均成立。
研究结论：
令人意外的是，兼具直接防御、间接防御与吸引功能的花部倍半萜类挥发物，而非葫芦素这类防御性状，似乎主导了葫芦科各类群与传粉者及花部植食者的互作关系。对于这类经济价值较高的作物而言，明确用于吸引与驱避的关键植物性状具有重要意义，尤其当传粉者与花部植食者共享相同的植物性状识别线索时更是如此。