Alaska has well over 2,500 named islands scattered along its coastlines and seashores. But there are likely far more “sky islands” contained inland. The ecological idea of a sky island is not new—a sky island is an isolated place, usually on a rocky mountaintop, that is surrounded by a sea of vegetation—but studies of sky island small mammal populations in Alaska are relatively recent. And mammalogists have much to learn.

“What we know about Alaska’s small mammals is about 100 years behind research of mammals in the Lower 48,” explains Link Olson, a biologist who splits his time and talent between the University of Alaska Museum of the North and UAF’s Department of Biology and Wildlife. Together with a team of graduate students and colleagues, Olson studies the population histories of small mammals throughout Alaska’s sky islands. And although his scientific question seems fairly straightforward—where are the mammals and how did they get there?—the tools for finding the answers are not so simple.

Small mammal research in Alaska is just plain hard, and there aren’t many scientists funded to do the work. For starters, sky islands are not easy to get to. Researchers climb mountains, float rivers, and fly in bush planes to get to the study sites during the short summer research season. As a result, today’s scientists have analyzed very few of the sky islands dotting Alaska for signs of small mammal populations.

Because of such limited access to these locations, researchers are forced to get creative with their resources. Olson’s group often uses a combination of historical museum specimens, animals collected recently in the field, and modern genetic analysis to piece together the history and current state of Alaska’s small mammal populations (“small” generally meaning smaller than a wolf).
Each of Olson’s students typically focuses on one species. Together, the group is reconstructing the evolutionary history and modern distributions of various small mammal populations throughout the state, including the collared pika and the Alaska marmot.

Alaska’s collared pika (Ochotona collaris) is a territorial, fist-sized relative of the rabbit that hates heat and forages very close to the alpine rocks where it lives. Looking at pictures of pikas, they are hard not to describe with a high-pitched voice as simply very cute. But there are more to these critters than their good looks.

Olson’s Ph.D. student, Hayley Lanier, is investigating where the current populations of Alaska’s collared pikas came from, and what they can tell us about historical climate change.

All of Alaska’s modern collared pikas live south of the Yukon River, but the population is split into two distinct locations—one eastern and one western set of sky islands. Lanier suspects that the two pika populations were divided at least 12,000 years ago by low-lying ice sheets during the Pleistocene glaciations, and that the animals have since lived and evolved as isolated populations.

To confirm her suspicions, grants from the National Science Foundation and the Alaska Department of Fish and Game allowed Lanier to look at the genetic variation among the two populations. The amount of genetic variation can indicate how distinct populations are related and when they last shared a common ancestor. Lots of genetic differences means the two groups are distantly related because their genes have had lots of time to mutate and change. Less genetic variation suggests that populations are more closely related because they haven’t had time to distinguish themselves. 

Examining the mitochondrial DNA from about 150 museum and field specimens from the east and west sky islands, Lanier discovered that Alaska is home to two genetically distinct pika populations. But at the same time, the two populations are genetically similar enough that they clearly came from a single ancestral population.

This common ancestor may have crossed into Alaska from Asia, where 28 of the world’s 30 pika species live. Or, the ancestor may have migrated to Alaska from the southern United States, where the second North American pika species—the American pika (Ochotona princeps)—currently lives.
In previous work, published in the latest issue of Molecular Phylogenetics and Evolution, Lanier and Olson used genetic studies to show that the collared and American pika species split much earlier than previously thought: 4.6 million years ago as opposed to the last 100,000 years. This revision in time suggests that climate-induced glaciations may have been responsible for the development of the two pika species in North America.

Continuing her current work, Lanier suggests that a population of the two species’ common ancestor may have wandered north (into what is now Alaska, the Yukon Territory, and British Columbia) in search of colder annual temperatures, and that this population became isolated from the more southerly distributed population, eventually resulting in two reproductively isolated species. But this cannot yet be determined.

Understanding exactly how climate may have moved North American pikas in the past may be the key to saving the species in the future. “It is widely accepted that the general warming trend in the world’s climate is having a negative impact on alpine specialists, such as pikas,” explains Lanier, “Already, the disappearance of pika populations throughout the western United States is attributable to climate change.”

The decline of the American pika, for example, has already lead many nonprofit groups to lobby for its protection under the federal Endangered Species Act. To facilitate a similar monitoring process in Alaska, Olson and Lanier are documenting as many populations of collared pika as possible, as well as their genetic distinctiveness. 

“Knowledge of where a species naturally occurs is the foundation of species management and conservation,” says Olson. “That baseline information can be coupled with genetic studies to allow us to monitor and hopefully preserve the most distinct and threatened populations.”

The Alaska marmot (Marmota broweri) is a fat, housecat-sized mammal that inhabits the sky islands of the Brooks Range and just a few other known spots north of the Yukon River. It is one of three marmot species in the state of Alaska—the hoary marmot (Marmota caligata) and the groundhog (Marmota monax) are the other two—and it only recently put itself on the map. Literally.

Until this year, distribution maps of marmots in Alaska lumped the hoary and Alaska marmots into one fuzzy group sweeping across much of the state, from the mountainous regions of the Southeast all the way to the Brooks Range. Although the hoary and Alaska marmots look very similar, they are genetically distinct and not at all closely related. Aren Gunderson, who received his M.S. from UAF in 2007and is on staff at the University of Alaska Museum of the North, refined the distribution maps of the hoary and Alaska marmots in a paper published in the August 2009 issue of the Journal of Mammalogy.

Over the course of three summer field seasons, funded largely by the Alaska Department of Fish and Game, Gunderson and his colleagues collected 27 new Alaska marmot specimens from the Brooks Range and a few more southerly sites in Alaska. His genetic analysis of these specimens revealed that Alaska marmots in the western Brooks Range recently colonized that area, while marmots in the eastern Brooks Range and in the Ray Mountains have persisted there for a longer period of time. This pattern of persistence in unglaciated areas and subsequent expansion into previously glaciated regions, as the glaciers retreat, has been observed in many Alaska mammals.

Gunderson discovered that the western Brooks Range population had the least amount of genetic variation, and therefore is likely the newest of the three population groups. Researchers now have a better idea of where the Alaska marmots live, but exactly when they arrived and where their populations originated have not yet been determined.

Gunderson explained his work with Alaska marmots to a broad audience when National Public Radio’s Michael Feldman recorded a live show of Whad’Ya Know? in Fairbanks and invited Gunderson to be one of his on-air guests. Feldman described Gunderson as a “one-man marmot encyclopedia” and asked if he climbed into the burrows after the marmots (he does not). With any luck, Alaska’s marmots will continue to catch some of the spotlight.

It looks like 2009 was a big year for the Alaska marmot. Not only did Olson and Gunderson publish more-accurate population maps for the scientific community, but the Alaska State Legislature officially dubbed February 2 “Marmot Day,” ousting the more common groundhog, a close relative, from holiday fame.

“The bill states there are no groundhogs in Alaska,” explains Gunderson, “implying that marmots deserve the spotlight.” A lovely sentiment, he says. But one that is factually wrong.

“Alaska actually does have groundhogs,” says Gunderson. “They are one of the three species of marmot in the state. We have Alaska marmots, hoary marmots, and groundhogs—but they are all marmots.”

Gunderson and his colleagues called and wrote to the author of the bill, but received no response. The bill consequently passed with the inaccurate groundhog information.

Ironically, rather than stealing the fame from the groundhog, the creation of “Marmot Day” actually creates a more marmot-inclusive holiday. It seems that there is more than one way that Olson and his team are helping to put Alaska’s small mammals on the map.