The word Beringia usually conjures up images of a landscape in the far northern reaches of the continent, perhaps of a grassy plain with mammoths grazing upon it. But a Yukon botanist thinks that Beringia might once have stretched much further south than anyone ever thought, and he's looking for proof among the plants in the southeast Yukon.

During the last ice age, Beringia was a refuge from the massive glaciers that covered most of the continent. When lower sea levels exposed the floor of the Bering Sea, these unglaciated lands stretched from Siberia across Alaska and as far east as the Mackenzie River.

Both plants and animals took refuge in this area, and some species of plants are still found only in Beringia. Botanists have studied this unique vegetation for decades, and the unusual species there are well known.

Researchers have only just begun to study the vegetation of the southeast Yukon, and, almost as soon as they started pulling out their field guides there, they began finding species that were not expected in that corner of the territory.

For example, Porsild's Poa was known to grow on unglaciated mountains in the north Yukon, but only recently was it found on isolated mountaintops in the Mackenzies and in the southeast Yukon. This grass is quite distinct botanically as the male and female parts occur on different plants.

It had been assumed that these unusual species had been introduced into the area, but Bennett was not so sure. He was finding species from Beringia in very isolated areas in the southeast Yukon. Finally he began to see a pattern, thanks to a little pink flower called rosy pussytoes.

"It sort of came like an avalanche," said Bennett. "I was putting a talk together on rare plants in the Yukon, and while I was collecting papers for it, I saw all these unusual distributions. A paper on rosy pussytoes had a map that showed unglaciated sections that cut into the southern Yukon, and everything started falling into place."

The map showed an ice-free corridor extending down the east side of the Mackenzie Mountains which Bennett thought might be the link between Beringia and the unusual plants in the southeast Yukon.

This corridor was in the rainshadow of the Mackenzie Mountains, just as Beringia was in the rainshadow of the coastal mountains, a region too dry for glaciers.

"People are reluctant to say that anything could have survived in the miserable conditions in the Mackenzies. It was not glaciated but it was extremely cold and snowy, while Beringia had a dry steppe habitat," said Bennett.

"But I think of places like nunataks (rocky hills surrounded by glacial ice) in Kluane that are just covered in plants, and they exist in an extremely harsh environment. So it is possible that some plants may have survived the conditions or that sometime after the ice age plants migrated in."

Researchers have found an amazing variety of species in the southeast Yukon. Not only are there plants from the northern Yukon, there are also coastal ones like Devil's Club.

"This location is where species from the north met species from the south for the first time, after being separated for thousands of years by ice. It is a very interesting convergence of species," said Bennett.

He feels some urgency to explore the plants of the southeast Yukon quickly as increased development in the valleys there has already wiped out some of the unusual finds. One researcher found a wild pea that also grows on the steppes of Mongolia, but the only known population of it disappeared after a road was widened in the area.

Bennett hopes that a type of rye grass will prove his theory about the link with Beringia. In remote areas of the Beaver and the La Biche Rivers, he has found Siberian Wild Rye growing in eroding riverbanks. As this is the plant's preferred habitat, Bennett did not think that the rye was invading the area as a weed.

Bennett has collected samples of the grass from different areas and will look at their genetic codes to see how closely they are related. His study, part of a pilot project with the University of Alaska, is using a new genetic-typing technique.

If he can prove his theory, it will add to our understanding of the glacial history of Beringia and the southeast Yukon. Bennett also points out that this work takes questions about Beringia back to their proper botanical roots.

A Swedish botanist, Eric Hultén, first coined the term Beringia in the 1930's when he was trying to match plants between the coasts of Alaska and Siberia. Bennett hopes his own work will help remind people that there is more to Beringia than woolly mammoths on the coastal plain.

For more information about Yukon plants, call Bruce Bennett with the Canadian Wildlife Service, Environment Canada, in Whitehorse at (867) 393-6700.