By Lee Newspapers

Before Europeans arrived in North America, bison are believed to have ranged from Alaska in the north to Mexico and from the Great Basin in the west to the Appalachians — a distance of more than 5.8 million square miles, or about two-thirds of the continent.

Despite the vast distance separating the herds, scientists have now calculated that the animals were closely related at the genetic level, highlighting the species’ ability to wander across vast landscapes.

The study “Paleogenomic insight into the collapse, recovery, and management of American bison” was recently published in the journal Science. Lead author Jonas Oppenheimer, of the University of California, Santa Cruz, collaborated with Montana and Wyoming scientists Craig Lee and Larry Todd, along with Parks Canada and many others, on the unusual research.

“This was highly interdisciplinary research involving many people, including evolutionary biologists, bison managers, archaeologists, and museum professionals, all working together to better understand how bison got to where they are today, and what this means for their future,” Oppenheimer said in an email. “We hope that this study might be an example of how paleogenomics can be used to facilitate wildlife restoration.”

The study was based on analysis of 160 bison genomes from across North America spanning the last 20,000 years. Think of genomes as the instruction book for building an animal, including the small pieces of DNA that tell genes things like hair and eye color.

“The advances in methods of both DNA analysis and (accelerator mass spectrometry) dating from when I started studying Plains bison sites are mind-blowing!” Todd said. “The data presented in this paper would not have been possible in the last century.”

“Frankly, this kind of work still boggles my mind,” Lee said in an email.

Oppenheimer said DNA provided a “direct window into the past,” allowing the researchers to “understand how being driven nearly to extinction impacted bison.”

“This had been difficult to address looking only at modern genomes, and led to a few surprises.”

Ancient bison bones

The Wyoming and Montana scientists contributed ancient bison samples for the research work.

Lee’s contribution to the research was providing samples for analysis. An assistant professor in Montana State University’s Department of Sociology and Anthropology, Lee has become well-known for his research at high elevations, called ice-patch archaeology. The exciting field has revealed human and animal occupation in places like the lofty Beartooth and Absaroka mountains in Montana and Wyoming that were previously believed to be largely ignored by Native Americans.

Ancient bison bones Lee recovered as ice patches melted were “important for establishing what the bison genome looked like prior to the arrival of European cattle genes,” he said.

Given his field of research, Lee said the Science study provides a “really powerful” argument for the importance of old collections and how they can be utilized to tell new stories.

“The remains of ancient bison are not just records of the past; they provide a baseline — maybe even the baseline — for informing modern conservation,” Lee said.

“To me, that really speaks to the importance of preserving archaeological and museum collections for the long term,” he continued. “Future researchers will undoubtedly ask questions far beyond our current ken. Basically, they will ask — and answer — things that we can’t even imagine.”

Bison nearly exterminated

The next big change for plains bison came with the arrival of Europeans. In less than 100 years, the once widespread mammals, the largest in North America, were nearly exterminated largely by market hunters killing the animals for their hides.

The systematic slaughter, aided by the U.S. military, also eliminated an animal crucial to many Native Americans’ way of life, spiritually and as a prime source of nutrition.

This massacre coupled with disease and habitat loss reduced the bison population so severely, estimated at fewer than 1,000 animals, that a genetic bottleneck was created, limiting the species’ diversity.

“Despite its dramatic scale, the 19th century bison population bottleneck appears not to have resulted in a reciprocal loss of genetic diversity,” the Science researchers wrote.

“Had it not been for the interest of a few private citizens in raising bison in captivity and the small wild populations found in Yellowstone National Park and Alberta, Canada, bison would be extinct today,” according to the National Park Service.

Few cattle genes found in bison

Roughly two dozen bison avoided slaughter in Yellowstone’s Pelican Valley. Supplemented by bison from other remnant herds, in the early 1900s the Park Service began rebuilding the park’s bison population.

Some of these remnant herds were also interbred with cattle. Yet the new research found low levels of hybridization, around .07 to 1.79 percent, and traced most of the interbreeding back about 20 generations when bison hit their low point.

“Together, these results suggest that cattle ancestry is much less common than previously thought and could potentially be lost over time through drift, as long as gene flow between herds is frequent enough to prevent particular segments of cattle ancestry from becoming fixed within herds,” the researchers wrote.

“Some groups, including Yellowstone-origin bison and all wood bison, had no evidence of cattle introgression,” the study found. However, “All modern wood bison have evidence of plains bison introgression stemming from 1920s translocations of plains bison into Wood Buffalo National Park.”

Todd was pleased by the findings.

“Ever since I began working with archaeological bison sites in the 1970s, I have been repeatedly told how much cattle interbreeding had impacted contemporary bison,” he said. “It’s exciting to now learn that this was more story than fact.”

Modern herds more isolated

However, after examining 52 previously published modern bison genomes, researchers found that today’s isolated herds are more genetically differentiated because of drift, inbreeding and limited gene flow.

“This fragmentation is the most striking way that present-day herds differ from past populations,” Oppenheimer said.

He added that restoring gene flow between today’s herds should be a priority for future restoration.

“The paper makes a really powerful genomic/conservation argument: ancient genomes show that past bison populations were broadly connected across North America through gene flow, whereas many modern herds are now highly structured because of the near-extinction bottleneck, isolation, and management history,” Lee said.

It’s now estimated there are about 20,500 Plains bison in conservation herds, according to the U.S. Fish and Wildlife Service, with about 420,000 in commercial herds.

The study’s findings support “reconnecting fragmented herds” to “help restore historical gene flow and strengthen bison resilience to future environmental change,” according to a Science press release.

“More generally, these ancient bison genomes add yet another perspective on the deep history of bison in North America,” Oppenheimer said.