Wild African fruit flies offer clues to their modern-day domestic life

December 6, 2018, Cell Press
A fly on marula fruit. Credit: Marcus Stensmyr

The fruit fly Drosophila melanogaster is quite possibly the most studied organism on the planet. Fruit flies are also quite familiar residents in many of our kitchens, attracted as they are to the fruit bowl. But how do the flies live in the wild? Surprisingly little is known.

Now, researchers reporting in Current Biology on December 6 on their studies of fruit flies living in their ancestral forests of Zimbabwe offer new clues into how the flies live in the wild. The story centers on the African marula fruit, which has a thick rind surrounding sugary pulp, similar to D. melanogaster's modern-day favorite of citrus. Their discoveries also help to explain how the fruit flies might first have been domesticated.

"The flies in your kitchen are the direct ancestors of a group of flies that lived on marula in a distant forest," says Marcus Stensmyr of Lund University in Sweden. "Some 10,000 years ago, these flies moved in with their human neighbors, and their offspring then colonized the world. That's pretty cool!"

Prior to the new study, D. melanogaster had never been observed from undisturbed wilderness. So, researchers led by Stensmyr and first author Suzan Mansourian set out to find the ancestral African home of this important model organism.

Using traps, they managed to locate wild flies in forests of Southern-Central Africa. Traps places in the vicinity of marula fruit trees quickly filled up with fruit flies. Traps placed in other parts of the forest collected little to no Drosophila. The researchers also showed that the fruit flies preferred marula fruits over citrus, a well-known favorite of theirs in other parts of the world.

When in season, "the flies are solely found with a single host fruit, marula," Stensmyr says.

In fact, the researchers found that D. melanogaster from other parts of the world still prefer marula over citrus, despite the fact that they've surely never seen it before. The flies are attracted to the main chemicals released by marula, which activate odorant receptors known to influence their selection of good spots to lay eggs.

One of the reasons the new discovery is especially intriguing is that marula fruit is not only of importance to flies. The fruit also has long-standing cultural significance to San people, who live in the region.

Archeological excavations of the caves where the San tribe lived during the Late Pleistocene to Early Holocene have uncovered enormous quantities of walnut-sized marula stones, which contain the seeds of the fruit. At least 24 million marula stones have been recovered from a single cave, the researchers note.

"The San evidently spent considerable time collecting and processing marula, which would have been the staple food item during many months of the year," the researchers write. "Thus, just like D. melanogaster, these San tribes appear to have been seasonal specialists on marula as well."

They propose that this may explain how first came to live among humans, attracted to them by the scent of marula. Once inside the caves, the flies would surely have benefitted from protection from predators and bad weather. Over time, the researchers suggest, the cave flies adapted, becoming more willing to enter dark enclosures and increasingly tolerant of ethanol.

"The fly has always been considered an opportunist and generalist, feeding and breeding in all manners of fruit," Stensmyr says. "In its native environment, however, the flies show a quite specialized lifestyle, being only found with marula fruit."

Stensmyr says they'll now go back to the forests of Africa, to "really figure out what the flies are doing in their native habitat."

Explore further: Fruit flies fear lion feces

More information: Current Biology, Mansourian et al.: "Wild African Drosophila melanogaster Are Seasonal Specialists on Marula Fruit" https://www.cell.com/current-biology/fulltext/S0960-9822(18)31362-9 , DOI: 10.1016/j.cub.2018.10.033

Related Stories

Fruit flies fear lion feces

May 30, 2018

A new doctoral thesis from Lund University in Sweden shows how fruit flies use their sense of smell and humidity to find food, avoid dehydration and discover the best place to lay their eggs—in overripe marula fruits. Faeces ...

Video: How to catch fruit flies

October 18, 2018

You can catch more flies with honey than with vinegar—or can you? In this video, Reactions explains the chemistry behind why fruit flies love vinegar so much that some entomologists call them "vinegar flies":

Love is in your guts

September 5, 2018

If you've ever had a gut feeling about a relationship, there may be more science behind it than you realise.

Those fruit flies are pickier than you think

December 5, 2013

On your kitchen counter, it might seem as though fruit flies will show up for just about any type of fruit you leave around for them. But when given a choice about where to lay their eggs, those flies will go for citrus most ...

How to kill fruit flies, according to a scientist

August 9, 2017

As a researcher who works on fruit flies, I often get asked how to get them out of someone's kitchen. This happens to fly researchers often enough that we sit around fly conferences (these actually exist) and complain about ...

Recommended for you

Rice plants that grow as clones from seed

December 12, 2018

Plant biologists at the University of California, Davis have discovered a way to make crop plants replicate through seeds as clones. The discovery, long sought by plant breeders and geneticists, could make it easier to propagate ...

Researchers find positive visual contagion in Barbary macaques

December 12, 2018

A pair of researchers at the University of Roehampton has found that captive Barbary macaques are capable of engaging in positive visual contagion—a behavior normally only seen in humans. In their paper published in Proceedings ...

Tiny tech tracks hummingbirds at urban feeders

December 12, 2018

Beep" is not a sound you expect to hear coming from a hummingbird feeder. Yet "beeps" abounded during a study led by the University of California, Davis to monitor hummingbirds around urban feeders and help answer questions ...

The real history of quantum biology

December 12, 2018

Quantum biology, a young and increasingly popular science genre, isn't as new as many believe, with a complicated and somewhat dark history, explain the founders of the world's first quantum biology doctoral training centre.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.