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Fruit bats might not have the best eyesight, but they smell great when they sniff one.
Even in the dark of night, their brain’s scent receptors can bind to a whole range of specific smells that float in the air, allowing these tropical pollinators to stalk nearby fruit for a midnight snack.
In fact, we might have bats to thank for the spicy smell of peppers. Recent fieldwork in Costa Rica has now found evidence that pepper plants and short-tailed fruit bats have co-evolved over millions of years.
The researchers say the volatile organic compounds (VOCs), responsible for the scent of ripe peppercorns, appear to be uniquely adapted to the scent receptors of local bats.
The study is based on hundreds of hours of work spent researching and collecting pepper plants in Costa Rica, before extracting the chemicals that form their scents.
In the end, the team was able to identify 249 VOCs among 22 plant species belonging to the Piper kind.
Some of the VOCs were common to all plants, such as the chemicals that form the spicy scents of cinnamon or cloves; other VOCs have only been found in a few species.
Each plant had its own bouquet of scents, but the authors had yet to determine whether that scent was suitable for a pollinator.
When researchers examined the droppings of three local fruit bat species – Carollia castanea, C. sowellii, and C. perspicillata – they found that all bats consumed a lot of pepper fruit, as suggested by previous research.
According to bat droppings, the fruits that gave off a rare VOC known as 2-heptanol were the ones that bats seemed to eat the most, along with two common VOCs found in almost all species of peppers: the α-caryophyllene or α-phellandrene. .
To further test these results, the researchers gave wild bats a choice between a normal unripe fruit from a pepper plant and an unripe fruit enriched with one of the three VOCs listed above.
Video recordings of the experiments add weight to the idea that wild bats are more likely to investigate and consume unripe fruit if they contain certain key scents that indicate maturity.
“These results suggest that bats use specific chemicals in the fragrant bouquet of fruit not only to select ripe fruit, but also to find the fruit. Piper species that make up the bulk of their diet, ”explains University of Washington biologist Sharlene Santana.
“By helping them communicate with bats, these chemical signals are likely a component of dispersal syndrome in these plants.”
Bats are important pollinators in tropical and desert environments. When these winged creatures eat the fruit, they poop elsewhere, dispersing the plant’s genes and increasing the diversity of the species.
Similar to how certain flower colors have evolved to attract hummingbirds, some scientists have postulated that certain fruit smells may have arisen to attract bats. But this is one of the first research to actually test whether fruits and bats really evolved together.
Careful statistical analysis of data from Costa Rica strongly suggests that the olfactory chemistry of pepper fruit and the diet of fruit bats are indeed related – a relationship that the authors say has contributed “to the extreme diversity of fruit bats. tropical fruit plants in the world “.
“Olfaction is the bridge between the plant signal and bat fruit consumption, and finding the specific VOCs that bats respond to opens the door to the pairing of odor receptor genes to important VOCs. , which was impossible until now, ”says Liliana Dávalos, ecologist and evolutionist. Stony Brook University.
The authors request further research to better understand how bats perceive VOCs and to what extent their affinity for odors is learned as opposed to innate.
The study was published in the Proceedings of the Royal Society B.
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