Relationship of visual and olfactory signal parameters in a food-deceptive flower mimicry system |
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Authors: | Galizia C Giovanni; Kunze Jan; Gumbert Andreas; Borg-Karlson Anna-Karin; Sachse Silke; Markl Christian; Menzel Randolf |
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Institution: | a University of California, Riverside. Department of Entomology 383, Riverside CA 92521, USA,b Institut für BiologieNeurobiologie, Freie Universität Berlin, Königin-Luise-Str. 28/30 D-14195 Berlin, Germany, c Ecological Chemistry/Organic Chemistry, Royal Institute of Technology, SE-100 44 Stockholm, Sweden |
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Abstract: | Pollinators such as bees are attracted to flowers by their visualdisplay and their scent. Although most flowers reinforce visitsby providing pollen and/or nectar, there are speciesnotablyfrom the orchid familythat do not but do resemble rewardingspecies. These mimicry relationships provide ideal opportunitiesfor investigating the evolution of floral signals and theirimpact on pollinator behavior. Here, we have reanalyzed a caseof specialized food mimicry between the orchid Orchis israeliticaand its model, the lily Bellevalia flexuosa. Based on currentknowledge of insect sensory physiology, we were able to characterizeboth the visual and olfactory signals of model and mimic, aswell as of two phylogenetically related orchids. By using acolor vision model, we mapped each species' visual signals tothe perceptual space of honeybees and found an apparent shiftof the mimic's visual signals towards the model. We confirmthat visual mimicry is present. We analyzed the flower odorsby using gas chromatography/mass spectroscopy. We related thesesignals to the perceptual space of the pollinators by testingthe scent extracts physiologically, using in vivo brain imaging.We found no evidence of olfactory mimicry. The results indicatethat evolutionary pressure acts on the visual, but not olfactory,traits of O. israelitica toward a higher similarity to its model.Apparently, odor mismatch does not prevent a bee from landingon a flower that has the expected visual display. The resultstherefore argue for the dominance of visual stimuli in short-distanceflower choice. The orchid may still depend on long-distanceolfactory attraction originating from neighboring model plants. |
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Keywords: | flowers mimicry olfactory signals Orchis israelitica visual signals |
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