NiCE: Olfaction in the Anthropocene: the effects of atmospheric pollutants on plant-pollinator interactions and the processing of floral scents

Human activities have drastically changed the environment, including the introduction of noise, light, and chemicals – termed sensory pollutants – that can be detected and processed by an animals’ sensory systems. Over the last twenty years, studies have repeatedly demonstrated the adverse effects of noise and light pollution on animal behavior, and there is growing evidence that chemical pollutants, like nitrate radicals (NO3) and ozone, can have similar effects.

However, few studies have examined how pollutant-enhanced degradation of scents affects the olfactory processing in the brain. Pollutants in the atmosphere, such as NO3, are thought to eliminate the ability of an insect, such as a pollinating bee or moth, to recognize the smell of a flower. Three-fourths of the world's flowering plants and about one-third of the world's food crops depend on animal pollinators for producing fruits, grains, and other crops.

Unfortunately, little is known about how different chemical pollutants, such as ozone, NO3, or hydroxy radicals (OH), may degrade certain chemicals in the scent, and how that, in turn, may influence behavior in different insect pollinators. Furthermore, how the degraded scent is processed in the pollinator’s olfactory system to suppress behavior is unknown.

Plant-pollinator systems are critical for ecosystem functioning and food security, and atmospheric pollutants give rise to smog and haze that severely impact human health. Using an interdisciplinary approach, this research will shed light on how these atmospheric processes affect olfactory and behavioral functions. The project will also introduce students to interdisciplinary research.

High School students in the Upward Bound Program will participate in the project through summer seminars and lab experiences. Finally, the project includes training undergraduates, graduate students, and postdoctoral associates and helps prepare them for independent scientific careers.

In the project, two pollinators, the nocturnal moth (Manduca sexta) and diurnal honeybee (Apis mellifera) will be used to examine the effects of daytime (ozone, OH) and nighttime (NO3) pollutants on diverse floral scents and determine how scent degradation affects neural processing in the primary olfactory system, the antennal lobe (AL). Behavioral assays, multichannel recordings, and state-of-the-art mass spectrometric approaches will be used to study the processing of degraded scents in antennal lobe circuits.

This will be accomplished with three Objectives: (1) Testing the hypothesis that daytime (OH, ozone) and night (NO3) atmospheric pollutants degrade diverse floral scents, and this chemistry affects specific compounds in the scents more so than others. (2) To test whether degraded scents influence the processing and balance of excitation and inhibition in the pollinator’s primary olfactory center, the antennal lobe (AL), and (3) using wind tunnel and common garden experiments with focal plant species, the hypothesis is that the degraded floral scents eliminate the pollinator’s ability to locate the flowers and reduce pollination. Together, these experiments may provide a basic framework for understanding the effects of scent oxidation and its processing in early olfactory circuits, and its effect on plant-pollinator interactions.

This project is supported jointly by Division of Integrative Organismal Systems in the Directorate for Biological Sciences of NSF and the Kavli Foundation.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.