Evol Ecol Res 10: 295-308 (2008)     Full PDF if your library subscribes.

Floral scents repel potentially nectar-thieving ants

Robert R. Junker and Nico Blüthgen*

Department of Animal Ecology and Tropical Biology, Biozentrum, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany

Author to whom all correspondence should be addressed.
e-mail: bluethgen@biozentrum.uni-wuerzburg.de


Hypothesis: Repellent floral volatiles are responsible for ants’ conspicuous absence from flowers.

Organisms: A broad spectrum of flowers (32 species for volatiles, 72 for nectar tests) was screened for their effect on different ant species.

Methods: The ants’ responses to floral scent bouquets and to individual floral volatiles were tested in a modified Pettersson four-arm olfactometer. Flower nectar was extracted with micro-capillaries and offered to ants to observe whether they accepted or rejected the nectar.

Results: While ants readily consumed almost all nectar offered to them, they were significantly repelled by a high proportion of floral scent bouquets. Repellent effects were confirmed for individual terpenoids commonly found in floral scents. Repellent floral scents provided an unequivocal explanation for the distribution of Formica rufibarbis ants among nectar-bearing flowers in situ.

Conclusions: This is the first clear demonstration that ant repellence from flowers is triggered by naturally emitted floral volatiles. This suggests that floral scents may function as allomones against enemies and not solely as synomones to attract mutualists.

Keywords: allomones, antagonists, floral traits, mutualism exploitation, nectar, olfactometer, repellence, terpenoids.

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