They found some snippets of the C. elephantopus genome in the population, and using a special computer model they analyzed how recently these genes would have entered the population. This would have happened when a living C. elephantopus mated with a C. becki — and is indirect proof that at that time living C. elephantopus existed.
They found that 84 of the tortoises had genetic indicators that one of their parents was a C. elephantopus, 30 of which were less than 15 years of age. Given the 100-year lifespan of the tortoises the researchers say there is a good chance that their C. elephantopus parent would still be alive.
"To our knowledge, this is the first report of the rediscovery of a species by way of tracking the genetic footprints left in the genomes of its hybrid offspring," study researcher Ryan Garrick, who performed the work at Yale University, but is now assistant professor at the University of Mississippi, said in a statement. "These findings breathe new life into the conservation prospects for members of this flagship group."
Because of genetic differences between the hybrid tortoises, the researchers estimate that at least 38 C. elephantopus left behind hybrid descendants on the Galápagos Islands, and many may still be alive.
If the researchers can find this hidden population, they could capture individuals to set up a breeding program to regenerate the species, the authors write in the paper published Jan. 9 in the journal Current Biology. They could even try to resuscitate the species from the genetic snippets found in C. becki.