General

Volume 37, Issue 2, 2018

Better Yields and Quality

Birds and bees can’t match the bat when it comes to pollinating pitaya

By Constance Tremlett


Fruits being sold at las 9 esquinas, a famous market in Guadalajara dedicated to the
sales of pitayas.
Courtesy of César Guzmán

Rows of cacti with huge white flowers frame the starry Mexico night sky. Against a backdrop of mountains, hundreds of bats zoom from flower to flower to shove their heads deep inside, feeding on the sweet nectar and pollen. Coyotes call in the distance. The cool air is refreshing after a hot day; the rains won’t arrive for another few months, and the valley is dusty and dry.

This is a typical evening for the cactus plantations in the Sayula Basin of Jalisco. The basin is a part of central-western Mexico renowned for the production of the pitaya—a delicious fruit harvested from these cacti. The pitaya (not to be confused with dragon fruit, the pitahaya) is economically and culturally important to the local economy. However, what a lot of people don’t realize is that bats are responsible for pollinating the flowers, allowing the pitaya to develop.

When thinking about pollinating animals, most people picture bees or other ‘buzzy’ insects. But in fact, bats are important pollinators of lots of plants, including many that people use for food. This especially holds true in the tropics. Some of the species that benefit from bats include several mango species, banana, cocoa, durian and agave. So, without bats we’d have no chocolate, tequila or pitaya!

Our research team—a collaboration between the University of Southampton, U.K., and CIIDIR Durango, Instituto Politécnico Nacional, Mexico—was lucky enough to spend the last couple of summers researching this interaction. The research took place in a small and welcoming community in Jalisco, Techaluta de Montenegro, whose town motto proudly reads: “The home of the pitaya.” Every year, town life is dominated by the production of pitayas, which mostly go on to be sold in the nearby state capital, Guadalajara. Locals commonly work 20 hours a day because, with a shelf life of only two days, the fruits need to be harvested, cleaned of spines, packaged carefully and sold all on the same day. The money generated goes a long way toward maintaining the entire town.

A bat visiting a flower: the principal pollinating bat species in the area is Leptonycteris
yerbabuenae, the lesser long-nosed bat.
Courtesy of César Guzmán

Experiments from our team showed conclusively that bats are essential for the production of these fruits. We placed bags of different mesh sizes over flowers at different times of day and night to expose the flowers to different pollinators. So, for example, the bags prevented birds and bees from accessing flowers during the day, but enabled bats to reach them at night—or vice versa. The fruits were then monitored to record fruit production and quality (fruit size and the number of seeds inside).

Not only was there more fruit when flowers were pollinated by bats instead of other animals, such as birds or insects, but the fruits were larger and had more seeds. As fruit size determines market price, bats are increasing both yield and quality of a crop that is important to the local economy. This emphasizes the urgent need for conservation of bat populations and increased awareness of the benefits that bats provide. A decline of bats or their pollination services would result in substantial loss of income for local communities, as well as the sad loss of such a delicious fruit!

Constance Tremlett is a conservation biologist, with a background in both practical conservation and ecological research. She is currently a Ph.D. student at the University of Southampton researching the ecological and economic benefits of bat pollination. This project is a collaboration between Dr. Kelvin Peh and Dr. Marije Schaafsma at the University of Southampton and Dr. Veronica Zamora-Gutierrez, a bat biologist at the Instituto Politécnico Nacional CIIDIR-Durango, Mexico.

 

 

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