Hunting for caribou ancestry

Source: Wikipedia Commons

Thursday, February 25th, 2010--

In the Canadian Yukon, scientists are using genetic techniques to identify caribou and to study ancient caribou that roamed the same ice patches 6,000 years ago. These woodland caribou live in small, threatened herds that are confined to northern Canada and Alaska. In addition to offering conservationists a novel tool for wildlife management, the research has revealed a link between certain caribou herds and a massive volcanic eruption 1,000 years ago.

Researchers from the U.S., U.K. and Canada have been collaborating since 1998, when ancient caribou bones and feces were found in high mountain ice patches. In the summer, caribou migrate from the valleys to high mountain areas where the snow doesn’t melt, seeking refuge from insects. Thousands of years of accumulated caribou droppings have effectively turned some ice patches black, says Tyler Kuhn, a graduate researcher at Simon Fraser University and an author of the study published this month in Molecular Ecology.

DNA was extracted from 40 caribou bone and teeth specimens, dating back to 6,000 years ago. This data was combined with data from modern DNA extracted from 395 individual caribou across 16 herds currently roving the southern Yukon. The scientists constructed a phylogeny - think of it as a family tree for a species - to track how genetically similar herds were across both geography and time.

The researchers found that the ancient caribou are related to the herds inhabiting the Yukon today, while their preserved droppings suggest they had a similar diet. However, three herds that currently inhabit the immediate area, the Southern Lakes, are genetically distinct. The DNA studies revealed that this population moved in and replaced the original herds roughly 1,000 years ago.

Around the same time, a massive volcanic eruption in the Wrangell Mountains in Alaska occurred, blanketing the area in a layer of ash, up to a foot deep, called the White River tephra. Tephra is any fragmented material produced by a volcanic eruption, be it ash or rock. “We believe that what happened is that the ancient caribou were displaced by this event, allowing a new unique caribou population to colonize the area,” Kuhn told Science Friday. He thinks the original herds may have moved further south, out of reach of the volcanic plume, and eventually had their place filled by the genetically distinct herds.

Kuhn is a native of Whitehorse, Yukon Territory’s largest city, which sits nestled between the Alaska Highway and Yukon River. He believes in the importance of understanding past population changes when considering conservation strategies, which is very much the case with the threatened woodland caribou. “Understanding the baseline from which to assess conservation strategies will be important,” says Kuhn. “Of course, for many species, this type of ancient genetic information isn't available.”

-Aleszu Bajak