UC Berkeley research study finds decline in genetic diversity of alpine chipmunks

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UC Berkeley researchers recently released a study chronicling the striking decline in the genetic diversity of alpine chipmunks, with all indicators suggesting that the decline is a consequence of global climate change.

The study, published Feb. 19 in the journal Nature Climate Change, compared the DNA of the species from 100 years ago to that of today’s alpine chipmunk and found a significant decrease in genetic diversity, an indicator of global warming’s vast reach that could impact the chipmunks’ long-term survival.

The study was not only scientific but also historical, as researchers compared modern-day data to research performed 100 years ago by Joseph Grinnell, the founding director of UC Berkeley’s Museum of Vertebrate Zoology.

“The beauty of the whole project is that we have this record of 100 years ago and a record of today, so we can compare across last century,” said James Patton, a co-author of the study and curator at the museum. “(We can now) make projections as to what will happen in 2050 (or) 2100, and that’s unusual — there aren’t very many data sets that have a historical capability and a modern capability.”

The researchers were able to draw upon the genetic material of Grinnell’s actual chipmunk specimens, preserved for a century in the archives of the museum, to make their comparisons.

A 2008 UC Berkeley study that drew on Grinnell’s research provided information for the current study as well. To celebrate the centennial anniversary of the museum, scientists returned to the sites Grinnell studied in the early 20th century — including Yosemite National Forest, the habitat of the alpine chipmunk —  to look for what changed.

They discovered that many species that were present at certain sites in the past were no longer there. Many lower-elevation species, including the alpine chipmunk in Yosemite, expanded their elevational range upward in a desperate bid to find a cooler environment. The average temperature in the park has increased more than 5 degrees Fahrenheit over the last century.

“(Grinnell) wrote a paper in 1910 in which he stated that the purpose of developing the museum really won’t be recognized for a century to come when the student of the future will have access to the records of the past,” Patton said.

Scientists are now benefiting from Grinnell’s meticulous records.

“I wanted to work on a project that paired historic and modern samples of chipmunks, (and it was) a great opportunity to examine changes in climate,” said Emily Rubidge, lead author and a graduate student in the department of environmental science, policy, and management while conducting the study. “It’s a simple, elegant study that shows something we expected.”

In addition to Rubidge and Patton, study co-authors include Craig Moritz, professor of integrative biology and director of the Museum of Vertebrate Zoology, and Justin Brashares, associate professor in the department of environmental science, policy, and management.

Rubidge began her research in 2005, predicting that there would be a loss of genetic diversity and an increase in isolation between populations due to the previous findings of elevational range changes. She compared the genetic diversity of the chipmunks to that of other species whose ranges did not change and found that their genetics had stayed the same over time.

“(This) reduced genetic diversity may be a threat to their long-term persistence,” she said in an email. “(It’s) a symptom of the environmental pressure these chipmunks are under.”

Sara Grossman covers research and ideas.