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Neural Basis of a Pollinator’s Buffet: Olfactory Specialization and Learning in Manduca sexta

Science  11 Jan 2013:
Vol. 339, Issue 6116, pp. 200-204
DOI: 10.1126/science.1225483

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A Varied Bouquet

Pollinators display innate attractions to odor, but can also learn to associate odor with a nectar reward. Riffell et al. (p. 200, published online 6 December; see the Perspective by Knaden and Hansson) characterized the odor profile for flowers to which hawkmoths are innately attracted and found that the majority contain a distinct chemical profile, which is uniquely represented on their olfactory lobe. The moths could also be trained to associate nonattractive odors with a reward and thus learn novel odor attractions. Though learning altered neurons within the antennal lobe, the innate preferences were not changed.

Abstract

Pollinators exhibit a range of innate and learned behaviors that mediate interactions with flowers, but the olfactory bases of these responses in a naturalistic context remain poorly understood. The hawkmoth Manduca sexta is an important pollinator for many night-blooming flowers but can learn—through olfactory conditioning—to visit other nectar resources. Analysis of the flowers that are innately attractive to moths shows that the scents all have converged on a similar chemical profile that, in turn, is uniquely represented in the moth‘s antennal (olfactory) lobe. Flexibility in visitation to nonattractive flowers, however, is mediated by octopamine-associated modulation of antennal-lobe neurons during learning. Furthermore, this flexibility does not extinguish the innate preferences. Such processing of stimuli through two olfactory channels, one involving an innate bias and the other a learned association, allows the moths to exist within a dynamic floral environment while maintaining specialized associations.

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