Here's one more reason to minimize car exhaust. Some pollinators may be having trouble finding their favorite flowers because the acrid smell of car fumes gets in the way.
Researchers from the University of Washington and University of Arizona have discovered that insects are in danger of not finding their source of food because the scents of other plants and environmental pollutants are preventing them from detecting the scent of nectar. Their findings are published in the June 27 issue of Science journal.
"Environmental volatiles, both natural and human-made, activate the same receptors that are activated by flower scents," explains Jeff Riffell, one of the researchers and neuroecologist at the University of Washington.
He says that when these receptors become exposed to strong odors that mask out the scent of flowers, the pollinators become used to these scents and stop being able to tell them apart. In other cases, Riffell says that the presence of other smells affect the way the insect's brain process the scent of nectar-producing flowers.
Riffell and his team focused specifically on the Manduca sexta or the tobacco hornworm moth, which has a sense of smell comparable to that of a dog, meaning they can distinguish different scents far better than humans. The Manduca sexta can fly up to 80 miles per hour in search of food and mates with a wingspan of up to four inches.
The researchers put the moths into a computerized wind tunnel that emitted various odors, including the fragrance of the Manduca's favorite flower, the trumpet-like sacred datura. The researchers also introduced a variety of other smells, including that of car and truck exhaust fumes and the creosote bush, a dense plant that smells like a blend of cherry soda and almonds and where the sacred datura likes to grow. They also inserted tiny 16-channel electrodes into the moth's brain to track its neuronal responses when exposed to various scents.
The findings, which surprised the researchers, revealed that moths lost their exceptional ability to find their food source because of the distracting odors.
"Local vegetation can mask the scent of flowers because the background scents activate the same moth olfactory channels as floral scents," says Riffell. "Plus the chemicals in these scents are similar to those emitted from exhaust engines and we found that pollutant concentrations equivalent to urban environments can decrease the ability of pollinators to find flowers."
While the results of the study are limited to the tobacco hornworm moth, experts believe the study has alarming implications for other pollinators, such as honeybees, bumblebees, butterflies and other kinds of moths, because the Manduca sexta is a popular insect model for study.
Biologist Alex Smith of University of Guelph in Ontario says the study highlights the dangers of human-induced substances that can disrupt natural ecological processes that contribute to the continuity of species.
"What this study suggests is potentially alarming for pollination and agriculture in general," Smith says. "What if the vast majority of species involved in pollination - about which we often know much less - are also affected in the same manner?"
