Giant tropical ants once roamed the North

Living in the far Northwest, it's all too easy for Yukoners to forget that the Bering Sea land bridge was not the only prehistoric dry route onto northern North America from other continents.

by Erling Friis-Baastad

Living in the far Northwest, it’s all too easy for Yukoners to forget that the Bering Sea land bridge was not the only prehistoric dry route onto northern North America from other continents. During some periods of the distant past, ancient flora and fauna could also have travelled to and from Europe across the De Geer route that connected Scandinavia with Greenland, and the Thulean route, which ran down from Iceland, through the Faroe Islands to Britain.

Among the many creatures that likely took advantage of those bridges across the Atlantic Ocean during the relatively hot, humid Eocene Epoch, around 55 to 35 million years ago, were giant, tropical ants, says Simon Fraser University paleoentomologist Bruce Archibald. And, he adds, the fossil record left by these ants may teach us much about changes we can expect now and in the future as the planet heats up.

For Archibald, the ant story really got underway during a visit to the Denver Museum of Nature and Science several years ago.

“I was looking through the collection in the museum and found this ant in a drawer there. I thought, ‘Oh, my, there’s a story attached to this guy.’”

Actually the guy was a gal, a queen Titanomyrma lubei. She’d been preserved in the fossil-rich Eocene lakebed sediments of the Green River Formation in Wyoming until an amateur collector, Louis Lube (hence lubei), found her and turned her over to a museum. Her rediscovery by a British Columbia palaeontologist set more research in motion. Archibald had read about fossilized giant ants found in Germany and on the Isle of Wight. Judging from the rich German fossil record, the ants, some up to seven centimetres long, once thrived in Germany.

Finding the huge queen in the US museum was an “Ah ha moment,” says Archibald. Somehow the ants must have travelled to Wyoming from Europe or to Europe from Wyoming. But that meant that a tropical creature would have had to make a long journey across the Canadian Arctic, which during the Eocene, was warmer than now, but not warm enough. Even the Arctic Eocene climate, which likely resembled that of the Vancouver area today, wouldn’t have supported the tropical ants.

“The difficulty is getting them up and over the highest latitude. If they’re heat-adapted organisms … the answer seems to lie in events we call hyperthermals,” says Archibald. Hyperthermals are especially hot periods within an epoch. Thanks to these events the idea of giant tropical ants, moving across what are now the territories of Nunavut, NWT and Yukon, whether east to west or west to east, began to make sense.

The North American fossil record for giant ants is scant: the Green River queen ant and one lone wing from Tennessee. “All we know is we see them on both sides of the Atlantic at a certain point,” says Archibald.  However, from studying contemporary ant behaviour he is able to inform his speculations as to how the ants travelled.

A queen would leave a nest, take to the air and be joined by winged workers in a nuptial flight, says Archibald, who stresses that queens and males from various ant communities would be in the air at the same time. After mating, the male would die and the queen would land and lose her wings. Then she’d look for a place to establish a new colony, underground, in rotting wood or in some other comfortable matrix, depending on species. Then she’d lay her eggs and start producing workers.

A young queen from that community would eventually go through the same process. This would be repeated again and again – over time extending the range of the species. The process is similar to that employed by trees when extending forests, says Archibald. “The important thing is you want to have your queen mating with males from different colonies, so you don’t get inbreeding,” he adds. So you have a whole population, not just one colony, extending its way across the Arctic down into then tropical Wyoming or up from Wyoming.

We don’t actually know much about how these tropical ants lived, says Archibald, so being able to state exactly what their environmental impact may have been on the northern ecosystems is restricted to speculation. “Climate change is like taking a big stick and stirring an environment around. Some things are going to benefit and some things are going to have a real hard time,” he says.

While these hummingbird-sized ants travelled, some other creatures became extinct. The scientist notes that skeptics will scoff and say, ‘Well, we’ve had global warming before, and we’re still here.’ But one has to wonder just who wants to endure the drastic change and chaos.

“It may be good for some things like West Nile Virus, but not good for other things,” he warns.

Was the arrival of Titanomyrma lubei bad news for other Eocene fauna? Did Yukon animals dread waves of carnivorous giant ants? Or did the ants feed on vegetation, scour the landscape and thus destroy food stocks relied upon by other creatures? Were the giant ants fungus farmers, as some ants are today? Different species of ants survive by a variety of methods so there’s no knowing for certain just yet, says Archibald. As well, the big juicy insects could have provided a bonanza of food for birds that would have caught them during nuptial flights, or for other creatures that might have discovered the ant nests.

Perhaps, as more of the Canadian Arctic is freed from ice, fossils of giant ants will be found there and questions answered. While global warming is definitely affecting the North, we are only just beginning to understand how much.

As for Archibald, he is moving on from giant ants to study other insect communities and has passed “the ant baton” over to Dr. Torsten Wappler, who will take advantage of ready access to the treasure trove of giant ant fossils in Germany.

For further information on these ants you can go to http:/brucearchibald.com and link free to a download of Intercontinental dispersal of giant thermophilic ants across the Arctic during early Eocene hyperthermals by S. Bruce Archibald et al in the Proceedings of the Royal Society.

This column is co-ordinated by the Northern Research Institute at Yukon College with major financial support from Environment Yukon and Yukon College/ The articles are archived at www.taiga.net/yourYukon.

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