When a population declines to a small number of survivors and then increases dramatically over the next few generations, there are always questions about genetic issues.
Meet Elisabeth Leung a student at the University of California at Riverside. Working with her advisor Professor Ellie Armstrong, Leung is “Exploring founder contributions from the captive island fox breeding programs for Santa Rosa and San Miguel Island using genomic sequencing.”
FIF is supporting Leung’s research because she is delving into an important question with long-lasting consequences for island foxes.
Around 26 years ago, the island fox populations on Santa Rosa and San Miguel Islands dropped to a critically low number: 15 surviving individuals on each island. When we look at Santa Rosa’s estimated population of 2,536 island foxes in 2023, all of them have descend from just 12 individuals in captive breeding: 4 males and 8 females.
Elisabeth Leung’s investigation will look directly at the genetics of the original founding individuals on Santa Rosa Island and San Miguel Island and compare their DNA to their descendants on the islands today.
Why is this important? Typically a population has some members with genetic-related health issues, maybe a tendency toward heart problems, a physical deformity, or an increased occurrence of specific cancers. Usually, these individuals are a small minority in the population because they are less successful passing on their genes before they die. When survivors are randomly chosen, rather than because they have traits that drive their success, traits that are not necessarily beneficial can increase across a population; this is called “genetic drift.”
With just 4 males contributing to the first generation of captive-born island foxes on Santa Rosa Island, if just one of those males carried a gene that increased health risks, a greater percentage of the population could be impacted. The recovered population might then have higher numbers of individuals with non-beneficial genetic traits. Overtime this would be expected to cause “inbreeding depression”–a magnification of negative traits and reduction in species vigor.
The Florida panther (Puma councilor coryi) is a well-known example of “inbreeding depression.” Genetic problems arose as the population became very small, leading to reduced male fertility and noticeably kinked tails. The inflammation response of Santa Catalina Island foxes to ear mite infestation may be linked to genetics or epigenetics and is currently being investigated by Alexandria DeCandia at the Smithsonian.
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| biologist examines island fox ear during health check |
Though geneticists have raised concerns about island foxes, there is no evidence of current genetic problems.
Today genetic research can delve deeper into DNA and health-related issues than it could 26 years ago. See FIF Grant for Transcriptomic Research
Leung’s research will help us understand the evolutionary impact of recovering from a small founding population. Has there been genetic drift in the fox populations on these two islands? What has changed or not changed in island fox genes?
To examine these changes, the lab at UC Riverside is also creating the first island fox reference genome. The island fox pictured here is fox “25205” on Santa Rosa Island. Blood samples from this island fox will be used to assemble the first complete island fox genome.
Genetic research has entered a golden age and donors like you are helping uncover important genetic information to help island foxes survive into the future.
