ManhattAnts

In the 21st century, most entomologists would head to a rainforest if they hoped to discover a new species of insect.

So, when biologist Rob Dunn taught at Columbia University, he did not expect to be greeted on the concrete jungles of New York City by an unknown critter. Still, Dunn scooped a few ants from the streets during breaks between classes because, I guess, that’s what curious biologists do. Oddly, the tiny critters he encountered did not appear to be like any members of the family Formicidae with which he was familiar.

He took a few back to his lab to have a closer look. Upon analysis, the ants Dunn had found in New York did not match any of the approximately 13,000 species known to myrmecologists. Shockingly, sitting in the biggest city in the United States was a potentially new type of ant.

They dubbed it the ManhattAnt.

This discovery wasn’t quite like one made in the Amazon, where scientists can be fairly certain a novel species had never been seen by humans before, due to the remote landscape. Though the ManhattAnt did not match anything in the database, this type had not been hiding in the sidewalk soil of the Big Apple for centuries unseen. Thanks to some similarities, Dunn and team were relatively certain this species had a lineage from Europe, though enough difference existed to separate them from anything in the Old World.

If they believed the ants had come from Europe, how could they be a new species?

Surprisingly, this phenomenon is not unique to this situation. We’ve investigated numerous times how physical barriers can produce endemic species. This effect is particularly striking on islands, such as the Galapagos or Christmas Island, where animals can be isolated for large swaths of time, but it can happen on land, too, as we learned with the Grand Canyon or White Sands National Park. Manhattan is an island, though it is far from isolated. Major urban centers can act as evolutionary islands, even if not surrounded by water. The spots that can support animal life in New York can be considered secluded islands, cut off from other similar species. In fact, New York has developed an endemic species of centipede, white-footed mouse, and sweat bee. So, it was not a far-fetched notion to believe an ant hitched a ride on a boat from Europe at some point in the past and slowly evolved into a distinct species.

Still, it was a surprise that no one had interacted with this ant in a place with so many people.

The ManhattAnt’s existence was not the end of the astonishments, however.

Since 2011, when Dunn discovered the ant in New York, scientists have used genetic sequencing to determine their ancestry. As it turns out, the ManhattAnt is not a new species; their genes have not drifted enough in isolation to earn a new scientific name. Instead, they are a species called Lasius emarginatus native to Europe and Asia Minor.

Their origin is not necessarily surprising, but what they’ve been up to in the decade-plus since Dunn first noticed them is odd. Like a crime family slowly extending its reach, the ManhattAnt did not sit idly in the 2010s and early 2020s. Laughing at the isolated centipedes, mice, and bees, the ManhattAnt moved into new territory, expanding more than a mile per year. They have arrived in Long Island and New Jersey. Biologists believe the ManhattAnt could end up, one day, as far north as Maine and as far south as Atlanta.

So, the ManhattAnt is just another invasive species looking for a new foothold. The bizarre part of this portion of the tale comes from the pedigree of the species. In Europe, where Lasius emarginatus has lived for millennia, the species is not dominant relative to other ants nor is it well adapted for urban existence. In other words, scientists would not have pegged the ManhattAnt with the ability to thrive in New York or to expand territory with other ant species on duty.

What allows the non-dominant, non-city-ready ants to thrive and expand in New York?

The ant jury is currently out on this question, though a few notions exist. First, the ManhattAnt seems to be good at climbing. Most ants do not enjoy going up on surfaces such as walls; this one, on the other hand, has shown up high in skyscraper apartments across the city. In a vertical wonderland, perhaps the ant who can climb can prosper. Further, somewhat counterintuitively for New York, they tend turn up their ant noses at human food. Instead, they love honeydew, a sugary excrement from aphids that proliferates in the trees of the city. Other species of ants do not chow down on insect poop, which means an abundant, easy food source for the ManhattAnt. This resource advantage could be enough to put this invasive ant into the ascendancy.

To date, the ManhattAnt has remained a curiosity, not causing any ecological disasters like some other invasives, such as the lanternfly. However, sometimes these alien species need time to wreak havoc; with the ability to spread up and down the Atlantic seaboard, the ManhattAnt could still outgrow its moniker and turn into a continental pest. Or maybe they remain true to their name and stay in the greater New York area, feasting on honeydew.