Trade-offs between pollinator attraction and florivore repellence in Tanacetum vulgare

• Applicant: Professorin Dr. Caroline Müller, since 4/2022
• Subject Area: Organismic Interactions, Chemical Ecology and Microbiomes of Plant Systems
• Term: from 2020 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 415496540

Floral volatiles occur in remarkable chemodiversity and attract insects over large distances, advertising nutritious nectar and pollen as rewards for flower visitors. However, in addition to mutualistic pollinating visitors, floral volatiles may also attract antagonistic florivores, leading to a trade-off. Tanacetum vulgare expresses chemotypes with distinct terpenoid composition in leaves and flowers. While leaf herbivores prefer specific T. vulgare chemotypes, little is known about chemotype-specific preferences of flower visitors. Flowers of T. vulgare depend on insect pollinators, but concurrently florivores like shining flower beetles (Phalacridae) feed on pollen and unripe seeds. Florivory may be prevented by expressing less attractive floral volatile patterns in older and pollinated flowers. This project aims to investigate potential trade-offs in floral volatiles which should attract pollinators but repel florivores. Chemotype-specific patterns of floral volatiles and metabolites in dependence of flower age and pollination status will be investigated. The chemical composition of leaves and phloem sap of the same plants and additional chemotypes will be analysed in P5 and P7, together allowing the calculation of chemodiversity indices and evaluation of phenotypic integration in P10. Furthermore, chemotype-specific pollinator and florivore choice behaviour will be explored. Behavioural observations in the greenhouse and field will be brought into context with the chemotype-specific behaviour of herbivores measured in P1–P5 and P7. Also, ecological consequences of plant chemodiversity on florivore and pollinator abundance and plant fitness, i.e. a potential trade-off and diversity benefit, will be elucidated and will contribute to the overall model developed in P9. It is expected that certain chemotypes are attractive and others repellent for both mutualists and antagonists and that flower age and pollination status are crucial for flower attractiveness. A common garden with mono-chemotype patches and mixed-chemotype patches will be established together with P5, with a similar design as used by P4. In mono patches flowers are expected to either rarely be pollinated or to lose seeds to florivores, whereas mixed patches may produce on average more seeds (diversity benefit). To obtain standardised genetic material (investigated in P8), clones of the five most common chemotypes found in the field will be used for all experiments in this project and P5. This project will provide insights in how chemodiversity benefits a plant in coping with simultaneous attraction of floral mutualists and antagonists. In a potential second project phase, the role of genetic diversity within the same chemotype for pollinators, florivores and their natural enemies may be investigated.

• DFG Programme: Research Units
• Subproject of: FOR 3000: Ecology and Evolution of Intraspecific Chemodiversity in Plants
• Ehemalige Antragstellerin: Dr. Elisabeth Johanna Eilers, until 3/2022