PUB - Publikationen an der Universität Bielefeld

**Background**
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. FVOC and pollen chemical composition may vary intra- and interspecifically. For certain pollinator and florivore species, responses towards 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. **Scope**
We reviewed how FVOCs and non-volatile floral chemical displays, i.e., pollen nutrients and toxins, vary in composition and affect the detection and behaviour of insect visitors. Moreover, we used meta-analyses to evaluate the detection of and responses towards FVOCs by pollinators vs. florivores within the same plant genera. We also tested whether the chemodiversity of FVOCs, pollen nutrients and toxins are correlated and hence mutually informative. **Key Results**
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 were a higher number of attractive than repellent compounds. FVOC and pollen toxin richness correlated negatively, indicating trade-offs, while a marginal positive correlation between pollen protein amount and toxin richness was observed. **Conclusions**
Plants face critical trade-offs, as floral chemicals mediate similar information to both mutualists and antagonists, particularly through attractive, and fewer repellent, FVOCs. Furthermore, florivores may detect more FVOCs, whose richness is correlated to reward chemical richness. FVOC chemodiversity is potentially informative of reward traits. To better understand 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 towards visitor responses.