Subversion of alarm communication: Do plants habituate aphids to their own alarm signals?

• Published in: Canadian journal of zoology Vol. 79; no. 4; pp. 737 - 740
• Main Authors: Petrescu, A.S, Mondor, E.B, Roitberg, B.D
• Format: Journal Article
• Language: English
• Published: Ottawa, Canada NRC Research Press 01.04.2001; National Research Council of Canada; Canadian Science Publishing NRC Research Press
• Subjects: (e)-beta-farnesene; Acyrthosiphon pisum; alarm pheromones; allomones; Animal and plant ecology; animal communication; Animal ethology; Animal, plant and microbial ecology; Animals; Aphididae; Aphids; Autoecology; Biological and medical sciences; defense mechanisms; Diseases & pests; disruption; dose response; Flowers & plants; Fundamental and applied biological sciences. Psychology; herbivores; host plants; Peas; pheromone habituation; Pheromones; Predation; Protozoa. Invertebrata; Psychology. Psychoanalysis. Psychiatry; responses; Chemical communication; Aphidoidea; Defensive secretion; Insecta; Defensive behavior; Interference; Acyrthosiphon pisum; Allelochemicals; Pest; Phytophagous; Homoptera; Animal plant relation; Arthropoda; Host plant; Aphididae; Alarm pheromone; Invertebrata; Semiochemicals; Adaptation
• ISSN: 0008-4301; 1480-3283; 1480-3283; 0008-4301
• DOI: 10.1139/z01-026

When attacked by a predator, pea aphids, Acyrthosiphon pisum, emit an alarm pheromone, (E)- β-farnesene, which causes nearby conspecifics to disperse from the area. However, herbivore-damaged plants also emit (E)- β-farnesene. We hypothesized that plants release farnesene to habituate aphids, i.e., to disrupt their alarm-pheromone responses, perhaps to reduce herbivory by increasing parasitoid or predator efficacy. Thus, we addressed two questions: (1) Do aphids habituate to (E)- β-farnesene, and (2) Are they habituated at levels produced by aphid-infested plants? On an artificial diet devoid of farnesene, aphids were exposed to 10 ng/cm 3 of (E)- β-farnesene or a hexane control over 24 h. Habituation was achieved, as dropping responses to 50 ng/cm 3 of (E)- β-farnesene decreased after exposure. We then exposed aphids to 0.8 ng/cm 3 of (E)- β-farnesene, a pheromone concentration emitted by plants, or a hexane control for 24 h. Their reaction to 38 ng/cm 3 of (E)- β-farnesene, the maximum pheromone concentration found in aphid-cornicle droplets, was not significantly different before and after exposure. Thus, our hypothesis that plants emit farnesene to disrupt aphid alarm communication remains unsupported.