A whimsical attempt to establish a herd of mouflon for sport hunting on a remote island in the Indian Ocean 50 years ago has inadvertently created a laboratory for genetic researchers and led to a surprising discovery.
A mouflon population, bred over dozens of generations from a single male and female pair transplanted to Haute Island from a Parisian zoo, has maintained the genetic diversity of its founding parents. This finding challenges the widely accepted theory of genetic drift, which states the genetic diversity of an inbred population will decrease over time.
"What is amazing is that models of genetic drift predict the genetic diversity of these animals should have been lost over time, but we've found that it has been maintained," said Dr. David Coltman, an evolutionary geneticist at the University of Alberta.
"We think this has happened because natural selection is more important to the evolutionary process than is commonly believed," he added.
Genetic diversity refers to the total amount of possible gene combinations that a mating male and female couple can produce. Scientists believe greater genetic diversity corresponds with greater odds of survival and successful reproduction due to a greater variety of genetic tools an organism has to combat the forces, such as diseases, that may otherwise weaken or kill it.
Coltman believes the harsh environment of Haute Island, with its cold winters, scarce resources and grass-borne parasites, has "kept the mouflon on their genetic toes, so to speak."
He argues that the extreme conditions on the craggy, windswept island have prevented genetic drift due to the premium advantage the more genetically diverse mouflon on the island hold over their less genetically diverse cousins.
"This herd certainly challenges our understanding of genetic drift," he said. "And I think it shows us the power of natural selection."