Geneticist and veterinarian Holly Ernest wanted to learn more about genetic variations in the elusive mountain lion. She posed the following question: "Mountain lions roam long distances--easily 30 miles in a single night. Do California mountain lions all interbreed, or do they have distinct populations in different geographic areas?"
Photo: Barb Delve
Ernest is in a unique position to gather such data. She works at the Veterinary Genetics Laboratory Wildlife and Ecology Unit, where she applies DNA technology to investigate genetic diversity, genetic patterns in populations, and the genetic basis of wildlife disease. Working with the School of Veterinary Medicine's Wildlife Health Center, Ernest and a team of wildlife biologists from university, state and federal agencies gathered DNA samples from 431 mountain lions. They analyzed significant DNA markers to determine the genetic structure of animals living in different regions around the state.
"In this study," Ernest states, "we were able to show that mountain lion populations in California are discrete, and -- by comparing genetic data -- learn that there are large genetic differences among regions in the state."
The team's findings have been reported in the journal Conservation Genetics.* Ernest is the principal author.
The role of genetic diversity in wildlife health
The California landscape offers multiple habitats for mountain lions, whose numbers are estimated at 4000 to 6000 by the California Department of Fish and Game. Yet researchers found that California's size, physical features, and human presence pose obstacles to mountain lion migration and breeding between identified populations. Ernest explains, "The DNA data also helped to define geographic barriers to migration and reproduction patterns, or gene flow, among members of the different populations."
Genetic variation within a species enables populations to adapt to changes in environment and other threats such as disease. When gene flow is diminished, animal populations become more inbred; and the species as a whole may have less of the genetic diversity that it needs to survive.
Wildlife experts keep a watchful eye on mountain lions (see other School of Veterinary Medicine mountain lion projects below). As Ernest puts it, "Mountain lions play a major role in ecosystems, as predators of federally listed endangered bighorn sheep, for example. Accurate information about these carnivores is essential for mountain lion conservation and the conservation of their prey."
"Knowledge of the genetic structure provides a foundation on which to evaluate whether certain populations may be threatened with inbreeding and what impact this could have on the species as a whole," Ernest adds.
Mountain lion populations must also be managed to minimize conflicts with humans.
Geographic barriers such as the San Francisco Bay, the Central Valley, and the Los Angeles Basin appeared to discourage interbreeding. The low, flat, and highly agricultural Central Valley, for example, separates two long mountain chains, the Coast Ranges and the Sierra Nevada, where animals showed enough DNA differences for scientists to conclude that the animals do not interbreed.
Although separated by relatively few miles, a partial barrier to gene flow also appears to exist along the crest of the Sierra Nevada. Mountain lions from the Yosemite region on the western side of the crest, researchers note, showed distinctly different genetic patterns than did their counterparts in the Round Valley on the eastern slope.
Mountain lions in coastal regions were found to have less genetic diversity than those inland, while estimated gene flow was high among mountain lions of the Modoc Plateau, the western Sierra Nevada, and the northern section of the eastern Sierra Nevada.
Mountain lion habitat and humans
Migration patterns of mountain lions have changed significantly as people have moved to rural areas. Researchers expressed concern that projected loss or fragmentation of habitat to human settlement in Southern California and the foothills of the western Sierra Nevada may reduce gene flow and isolate mountain lion populations.
The authors conclude that mountain lion management and conservation efforts should be individualized according to each region's distinct population. The study results also indicate that preservation of existing movement corridors among regions could prevent future population declines and loss of genetic variation.
* "Genetic structure of mountain lion (Puma concolor) populations in California." Holly B. Ernest (Veterinary Genetics Lab), Walter M. Boyce (School of Veterinary Medicine, Wildlife Health Center), Vernon C. Bleich (California Dept of Fish and Game), Bernie May (UC Davis Dept of Animal Science), San J. Stiver (Nevada Division of Wildlife), & Steven G. Torres (California Dept of Fish and Game).
The UC Davis Genetic Resources Conservation Program, UC Division of Agriculture and Natural Resources, California Dept of Fish and Game, UC Davis Jastro-Shields Scholarship and School of Veterinary Medicine fellowships, and the American Museum of Natural History's Theodore Roosevelt Memorial Fund provided funding for this study.
To read articles about how DNA techniques are used for mountain lion research, see Outdoor California May-June 2000. Copies may be obtained by calling (916) 653-7664, or by downloading from the link below:
Learn about mountain lion studies of the Southern California Ecosystem Health Project at the School of Veterinary Medicine's Wildlife Health Center.
Contacts: Holly B. Ernest, Associate Director, Wildlife and Ecology Unit, Veterinary Genetics Laboratory
Lynn Narlesky, Communications, School of Veterinary Medicine