Island foxes may be 'least variable' of all wild animals

Date:April 21, 2016

Source:Cell Press

In comparison to their relatives on the mainland, the Channel Island foxes living on six of California's Channel Islands are dwarves, at two-thirds the size. The island foxes most likely evolved from gray foxes brought to the northern islands by humans over 7,000 years ago. Some think island foxes may have been partially domesticated by Native Americans. Like many island species, they have little fear of humans.

Now a new study reported in the Cell Press journal Current Biology on April 21 finds that the foxes also show a surprising absence of genetic variation. The study offers the first complete genome sequences of an island species that is a model for long-term conservation of small, endangered populations, the researchers say.

"We find a dramatic reduction of genetic variation, far lower than most other animal species," says Jacqueline Robinson of the University of California, Los Angeles (UCLA).

One population in particular living on San Nicolas Island has an order of magnitude lower variation than any other known species, including the severely endangered African cheetah, Mountain gorilla, and Tasmanian devil, she says. Such near absence of genetic variation doesn't bode well for the foxes. But it also presents a puzzle as to how the foxes have managed as well as they have.

"The degree to which the San Nicolas foxes have lost genetic variation is remarkable, upholding a previous observation that they may be the least genetically variable population of wild animals known," says Robert Wayne, also of UCLA. "It suggests that under some conditions, genetic variation is not absolutely essential for the persistence of endangered populations."

The researchers sequenced DNA samples representing each of the Channel Island fox populations and one mainland gray fox from southern California. Researchers originally collected the island fox samples back in 1988, prior to subsequent population declines due to predation and disease in four of the island populations

Theory holds that small populations will not only lose variation, but will also accumulate deleterious variation as the normal process of natural selection fails. Indeed, the complete genomes of the island foxes show dramatic, 3- to 84-fold declines in heterozygosity. (Heterozygosity refers to places in the genome where an individual has inherited different variants of the same gene from their mother and father.) The foxes also show sharp increases in genes for which they carried two copies of a variant deemed to be harmful or deleterious in some way.

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Island foxes may need genetic rescue

Date:March 21, 2016

Source:Colorado State University

The island fox has made a remarkable comeback from the brink of extinction, with three of six populations on their way to becoming the fastest mammal recovered under the Endangered Species Act. But new research published online March 17 inMolecular Ecology uncovers a hidden danger to the future viability of some island fox populations.

Chris Funk, associate professor in the College of Natural Sciences' Department of Biology, led the research team that conducted the largest and most in-depth genetic study to date of California Channel Island foxes. Funk is also director of the SoGES (School of Global Environmental Sustainability) Global Biodiversity Center at CSU. The study confirmed that each island's fox population likely warrants designation as a unique subspecies. But it also found that one subspecies, on San Nicolas Island, may require genetic rescue to reduce its risk of extinction.

The San Nicolas Island fox has the lowest genetic variation ever found in a mammal species, making them especially vulnerable. "Low genetic diversity may lead to lower survival and reproductive success, and may reduce the ability of a population to adapt to climate change or new, introduced diseases," Funk said. "With a dwindling population of fewer than 300 adults, actions need to be taken quickly to preserve this important member of the Channel Islands ecosystem."

The scientists say that if this subspecies' genetic health is poor, it may be necessary to use "genetic rescue," bringing island fox individuals from other islands to boost the San Nicolas gene pool. This approach has been successfully implemented in the past to save populations from extinction, including the resuscitation of the Florida panther back in 1995.

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'Dwarf' foxes, saved from extinction, make an incredible recovery

Stephen Messenger

Science / Endangered Species

May 28, 2013

While they may be a bit smaller than your average house cat, what these 'dwarf' Island foxes lack in stature, they make up for in resilience.

Not long ago, the future looked bleak for the distinctly diminutive fox species that reside on California's Channel Islands. In the mid-1990s, the island fox's numbers had plummeted from the thousands to, in some cases, just over a dozen -- raising alarms that the species would soon be extinct and prompting them to be classified as a 'critically endangered' species.

But now, after a few short years of incredibly well-executed conservation tactics, biologists say that the tiny canine has made one of the fastest recoveries of any animal in the history of the Endangered Species Act.

The history of the island fox's decline offers a lesson on the interconnectivity of nature. Bald eagles were once common along the Channel Islands, feeding mostly on fish while the foxes feasted on insects, birds, and other land mammals. Exposure to the now-banned insecticide DDT, which washed into the ocean and contaminate their diet, caused bald eagles to die off -- opening the skies over the islands for a new bird of prey to take hold.

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