The choice between flowers of closely related plant species by generalist pollinator: identification of relevant VOCs

Abstract

False blister beetles of the genus Oedemera (Coleoptera: Oedemeridae) are known as generalist pollinators of many plant species, but their mutualistic interactions are still insufficiently explored. The aim of the study was to identify the floral compounds emitted by sympatric and simultaneously co-flowering strawberry species that could serve for Oedemera beetles as olfactory cues of suitable flowers. In the test locality, flowers of Fragaria vesca and Fragaria viridis were visited by Oedemera lurida and Oedemera virescens beetles. O. lurida preferred flowers of F. viridis to those of F. vesca, whereas O. virescens tended to prefer F. vesca to F. viridis. GC-EAD analysis revealed that O. lurida perceived three compounds of F. vesca and four compounds of F. viridis flowers. Among these, nonanal, 2-phenylacetaldehyde and an unidentified compound (UC1) were common to both strawberries, while the amount of one compound (1,4-dimethoxybenzene) required to elicit an EAG response was sufficient in F. viridis, but not in F. vesca. Our results suggest that O. lurida are capable of choosing between flowers of the two strawberries based on VOCs’ with 1,4-dimethoxybenzene as a relevant key component. O. virescens responded to eight compounds present in F. vesca flowers. The flowers contained three compounds EAG-active towards O. lurida and O. virescens (nonanal, 2-phenylacetaldehyde, UC1) and five compounds EAG-active towards O. virescens only (acetic acid, decanal, (E)-non-2-enal, linalool, and UC2). In F. vesca and F. viridis flower extracts as well as headspaces, the identified compounds differed qualitatively only. (E)-Non-2-enal and acetic acid were recorded for the first time in Fragaria. Local specialization of Oedemera beetles in flower visiting was proved and relevant VOCs were identified.