Department of Chemical Ecology, Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany.
Department of Biology, Evolutionary Ecology of Plants, University of Marburg, Karl-von-Frisch-Straße 8, 35043 Marburg, Germany.
Ann Bot. 2023 Oct 4;132(1):1-14. doi: 10.1093/aob/mcad064.
Plants often use floral displays to attract mutualists and prevent antagonist attacks. Chemical displays detectable from a distance include attractive or repellent floral volatile organic compounds (FVOCs). Locally, visitors perceive contact chemicals including nutrients but also deterrent or toxic constituents of pollen and nectar. The FVOC and pollen chemical composition can vary intra- and interspecifically. For certain pollinator and florivore species, responses to these compounds are studied in specific plant systems, yet we lack a synthesis of general patterns comparing these two groups and insights into potential correlations between FVOC and pollen chemodiversity.
We reviewed how FVOCs and non-volatile floral chemical displays, i.e. pollen nutrients and toxins, vary in composition and affect the detection by and behaviour of insect visitors. Moreover, we used meta-analyses to evaluate the detection of and responses to FVOCs by pollinators vs. florivores within the same plant genera. We also tested whether the chemodiversity of FVOCs, pollen nutrients and toxins is correlated, hence mutually informative.
According to available data, florivores could detect more FVOCs than pollinators. Frequently tested FVOCs were often reported as pollinator-attractive and florivore-repellent. Among FVOCs tested on both visitor groups, there was a higher number of attractive than repellent compounds. FVOC and pollen toxin richness were negatively correlated, indicating trade-offs, whereas a marginal positive correlation between the amount of pollen protein and toxin richness was observed.
Plants face critical trade-offs, because floral chemicals mediate similar information to both mutualists and antagonists, particularly through attractive FVOCs, with fewer repellent FVOCs. Furthermore, florivores might detect more FVOCs, whose richness is correlated with the chemical richness of rewards. Chemodiversity of FVOCs is potentially informative of reward traits. To gain a better understanding of the ecological processes shaping floral chemical displays, more research is needed on floral antagonists of diverse plant species and on the role of floral chemodiversity in visitor responses.
植物通常利用花部展示来吸引互惠者并防止天敌的攻击。远距离可检测到的化学信号包括有吸引力或有驱避性的花部挥发性有机化合物（FVOCs）。在局部范围内，访问者可以感知到包括营养物质在内的接触性化学物质，但也包括花粉和花蜜中的防御性或毒性成分。FVOC 和花粉的化学成分在种内和种间都可能有所不同。对于某些传粉者和食花粉者物种，人们在特定的植物系统中研究了它们对这些化合物的反应，但我们缺乏对这两组化合物的综合比较，也缺乏对 FVOC 和花粉化学生物多样性之间潜在相关性的深入了解。
我们综述了 FVOC 以及非挥发性花部化学信号（即花粉营养物和毒素）在组成上的变化，以及它们如何影响昆虫访问者的探测和行为。此外，我们使用元分析来评估同一植物属中传粉者和食花粉者对 FVOC 的探测和反应。我们还测试了 FVOC、花粉营养物和毒素的化学生物多样性是否相关，从而相互提供信息。
根据现有数据，食花粉者比传粉者能探测到更多的 FVOC。经常测试的 FVOC 常被报道为传粉者吸引而食花粉者驱避。在测试过的两种访问者群体的 FVOC 中，有更多的吸引物而不是驱避物。测试过的 FVOC 和花粉毒素丰富度呈负相关，表明存在权衡，而花粉蛋白量与毒素丰富度之间存在边际正相关。
植物面临着关键的权衡，因为花部化学物质向互惠者和天敌传递相似的信息，特别是通过有吸引力的 FVOC，而有驱避性的 FVOC 较少。此外，食花粉者可能会探测到更多的 FVOC，其丰富度与报酬的化学丰富度相关。FVOC 的化学生物多样性可能与报酬特征相关。为了更好地理解塑造花部化学信号的生态过程，需要对不同植物物种的花部天敌以及花部化学生物多样性在访问者反应中的作用进行更多研究。
