Ozone Differentially Affects Perception of Plant Volatiles in Western Honey Bees

Abstract

Floral scents play a key role in mediating plant-pollinator interactions. Volatile organic compounds (VOCs) emitted by flowers are used by flower visitors as olfactory cues to locate flowers, both from a distance and at close range. More recently it has been demonstrated that reactive molecules such as ozone can modify or degrade VOCs, and this may impair the communication between plants and their pollinators. However, it is not known whether such reactive molecules also may affect the olfactory system of pollinators, and thus not only influence signal transmission but perception of the signal. In this study, we used electroantennographic measurements to determine the effect of increased levels of ozone on antennal responses in western honey bees (Apis mellifera L.). Linalool and 2-phenylethanol, both known to be involved in location of flowers by the bees, and (Z)-3-hexenyl acetate, a widespread green leaf volatile also detected by bees, were used. The results showed that ozone affected antennal responses to the different substances differently. Ozone decreased antennal responses to (Z)-3-hexenyl acetate, whereas responses to linalool and 2-phenylethanol were not influenced by ozone. Overall, the study does not provide evidence that pollination by honey bees is impaired by damage in the olfactory system of the bees caused by increased levels of ozone, at least when linalool and 2-phenylethanol are the attractive signals. However, the results also suggest that ozone can change the overall perception of an odor blend. This might have negative effects in pollination systems and other organismic interactions mediated by specific ratios of compounds.

Keywords: Apis mellifera; Atmospheric pollutant; Electroantennography; Floral and vegetative volatiles.

Fig. 1

Electroantennographic (EAG) responses (Mean ± SE) of honey bees to the three tested substances, with or without ozone fumigation during the 2nd sequence. None of the antennae were fumigated with ozone during the 3rd sequence. T: statistical treatment effect, S: statistical sequence effect, TxS: statistical interaction effect of T and S; outcomes of a repeated measures ANOVA are given as ns: non-significant (P > 0.05) or *: significant at P < 0.05. Solid and dashed grey lines show significant (P < 0.001) and non-significant (P > 0.05) effects, respectively, as indicated by post-hoc tests