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Beneath the feet of millions of New Yorkers, a species of ant – originally found nowhere else in North America – has flourished in the concrete jungle for more than a decade, surprising scientists with its unique ability to flourish in Manhattan and countries other of the city. borough. But it is still not a mystery where the insect came from and why this urban setting was so successful.
Now, scientists have discovered the identity and origin of the ant, and it is a few thousand miles from home. The globular insect, Lasius emarginatus, is a native European species commonly seen in more natural settings in central Europe, according to new research.
Researchers first spotted the insect, known as the “ManhattAnt,” while surveying ants in New York City in 2011. The ant — with its black head and red abdomen and thorax — did not match almost none. 800 species found in North America and the researchers speculated that it could be a European species; no further research was done to confirm the species at the time.
But now, the number of insects has increased so that it is the second most common ant in the area, attracting the attention of scientists and New Yorkers who live with the pest, said Clint Penick, assistant professor of entomology and of plant pathology at Auburn. University in Alabama.
Although entomologists keep a close eye on the non-native species to monitor its impact on the environment, they have several theories that explain how the ant made it to North America and why it is doing so well in the big city , according to a study. published May 28 in the journal Biological Invasions.
Start of invasion
A 2009 ant survey did not see the ManhattAnt, suggesting it arrived in the city soon after. Although it has called the Big Apple its home in North America for just over 10 years, the species is busy, spreading at a rate of about 2 kilometers (1.2 miles) per year.
So far, the insect has been observed on Long Island and in several New Jersey cities, according to the study. Based on the European climates in which insects can thrive, the authors suspect that the ant could go as far north as Maine and as far south as Georgia in the future.
“The species has more or less taken over Manhattan over the past decade,” said Penick, the study’s senior author. “It’s second most common to the sidewalk ant (Tetramorium imigrans), which has been (in New York) for at least a century.”
The invasive ants have so far spread naturally through mating flights — when winged ants fly away from the nest to form new colonies in the summer — but the authors predict the species will be able to spread further through vehicle transport , such as ships and cars, since it has become so dominant in a big city like New York, Penick said.
Such behavior is likely how the ants came to North America in the first place, said Corrie Moreau, a professor of biology and entomology at Cornell University, who was not involved in the new study.
“Many non-native or invasive species are inadvertently transported by people, usually in things like potting soil or sometimes in ship cargo,” but it’s less common for such insects to take hold and settle in their new habitat. environment, Moreau said, citing a 2005 study that found only 12% of previously introduced ant species established in their new locations.
Ants in the Big Apple
To identify the ManhattAnt species, the international team of researchers who worked on the May study first extracted DNA from the ants to compare with other species using a global database.
The genetic test confirmed that the ant belonged to the genus Lasius, but to identify exactly which species, the researchers sent specimens to co-author Bernhard Seifert, a leading ant researcher in Germany who studied the native European species. By comparing the New York ants to the European ones, Seifert was able to confirm the ant’s identity.
Because the non-native ants have become so common in New York City so quickly, the researchers initially suspected that the ManhattAnt shared a trait commonly seen in successful invasive ant species: the tendency to build super colonies formation. Supercolonies are very large colonies made up of nests that have been known to span hundreds of miles in some cases, Penick said.
“(Ants in super colonies) have very low aggression, and they’re just the blanket of the earth and they’re peaceful within their colony,” he said. Because the nests work together rather than against each other, they can spread more quickly and easily influence an area by competing with native species, he said.
But when the authors tested that hypothesis on the ManhattAnts by collecting specimens from different nests around the city and putting them together, they found that the ants showed aggression and fought with each other, a sign that these insects keep typical territories seen with regular colonies and not supercolonies.
With that theory out of the way, the researchers looked for other ways in which the ManhattAnts differed from other common ants in the area. They discovered that the Manhattan Ants, one of the only species regularly found on the sidewalks of New York, were using a specific food source within trees planted on the city’s streets – a sticky liquid substance on their Aphids and tree bugs secrete honey. as the saw lantern fly.
“It’s their ability to make that transition and use these urban structures and habitats (with food sources) that other ants can’t quite achieve that helps them be so successful in the city,” said lead author Samantha Kennett. of study and a doctoral student in the department of forestry and environmental conservation at Clemson University in South Carolina.
The ants have also been observed eating human food in some cases, but their European counterparts eat mainly other insects and their droppings, said Kennett.
Generally, the most generalist insects, Moreau said, are non-native insects that generally thrive, meaning they are not limited to a particular diet or certain environments. “Because (the Manhattan Ants) are more general, there’s a greater chance that they can land in a new place and be successful,” she said.
Impact on the ecosystem
The ManhattAnts are not harmful to humans, but like any insect they can be a nuisance when they end up in apartments, Kennett said. The ants were observed all the way up to the sixth floor of apartment buildings, according to the study.
The biggest concern, however, is the negative impact the ants may have on their environments, such as the trees they are planting, or the native species they may be competing with, which she said.
“One of the things we know about a lot of invasive ant species is that they displace the native species, and the native species that they’re displacing tend to have very specialized roles in the ecosystem, and as so you’re disrupting that ecosystem when you have these. species are introduced,” Moreau said.
“Maybe if (ManhattAnts) became the preferred food for birds, we wouldn’t be so upset about it. But we haven’t seen any ways in which they’re beneficial yet, so we don’t know,” she said.
The authors of the May study said that they hope that further research will identify other characteristics that the ants may have developed in order to succeed so well in their new home as well as to spread widely at present. Through the iNaturalist project, citizens can observe the insect by spotting the ants and taking photos to upload to the site.
Time will tell if the ant is more than a nuisance and is disrupting the ecosystem, Penick said.
“It’s not the worst thing in the world to deal with some ants in your kitchen,” he said. “I think that could be the worst we see. That’s really my hope.”
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