Yosemite's Alpine Chipmunks Take Genetic Hit From Climate Change

Global warming has forced alpine chipmunks in Yosemite to higher ground, prompting a startling decline in the species' genetic diversity, according to a new study by UC Berkeley researchers.

The study, which appeared Sunday, February 19, in the advance online publication of the journal Nature Climate Change, is one of the first to show a hit to the genetic diversity of a species because of a recent climate-induced change in the animals’ geographic range. What’s more, the genetic erosion occurred in the relatively short span of 90 years, highlighting the rapid threat that changing climate can pose to a species.

Yosemite Alpine Chipmunk

Climate change may be threatening the survival of the alpine chipmunk.
PHOTO: Risa Sargent

A species with low genetic diversity can be more vulner­able to the effects of inbreeding, disease, and other prob­lems that threaten species survival, the researchers said.

"Climate change is implicated as the cause of geo­graphic shifts observed among birds, small mammals, and plants, but this new work shows that, particu­larly for mountain species like the alpine chipmunk, such shifts can result in increasingly fragmented and genetically impoverished populations," said the study’s lead author, Emily Rubidge, who conducted the research while a Ph.D. student at UC Berkeley's Museum of Vertebrate Zoology (MVZ) and the Department of Environmental Science, Policy, and Management (ESPM). "Under contin­ued warming, the alpine chipmunk could be on the trajectory toward becom­ing threatened or even extinct."

Rubidge worked with Craig Moritz, professor of inte­grative biology and MVZ director; James Patton, profes­sor emeritus of integrative biology and MVZ curator; and Justin Brashares, associate professor in ESPM.

The new findings build upon previous research that found major shifts in the range of small mammals in Yosemite national park since the early 1900s. in 2003, biologists at UC Berkeley began an ambi­tious resurvey of Yosemite’s birds, mammals, rep­tiles, and amphibians, retracing the steps originally taken between 1914 and 1920 by Joseph Grinnell, the MVZ’s founder and former director (see Back Page for related story).

The Grinnell resurvey project, led by Moritz and museum colleagues, found that many small mam­mals in Yosemite moved or retracted their ranges to higher, cooler elevations over the past century, a period when the average temperature in the park increased by about 5.4 degrees Fahrenheit.

“Much of what we read and hear about the effects of climate change on biodiversity is based on model projections and simulations, and these models typically involve many moving parts and lots of uncertainty,” said Brashares. “Thanks to the base­line provided by Joseph Grin­nell’s pioneering efforts in the early 20th century, we are able to go beyond pro­jections to document how climate is altering life in California. The research led by Emily is novel and important because it shows empirically that cli­mate change has led to the loss of genetic diversity in a wild mammal over the last sev­eral decades.”

WEB EXTRA: Justin Brashares talks about emulating Jane Goodall, being chased up a tree by lions, and making the connection between European fisheries and African bushmeat markets. Read the interview in the inaugural issue of ESPM’s Our Environment newsletter.