Photo by Gary Bendig on unsplash
Researchers have uncovered how natural selection “rewilds” domestic rabbits.
A study published in Nature Ecology and Evolution explains how normally tame rabbits — which have many natural predators — can become a force of ecological destruction when purposefully or accidentally reintroduced to the wild.
As the story of Peter Cottontail illustrates, gardeners know rabbits can be a nuisance, but not everyone realizes the magnitude of ecological destruction rabbits can cause.
“The classic example is Australia, which was colonized by rabbits to the point that it caused one of the largest environmental disasters in history,” says Dr. Leif Andersson, a professor at the Texas A&M School of Veterinary Medicine and Biomedical Sciences.
“In 1859, an Englishman named Thomas Austin released 24 European rabbits onto his estate as game animals, but the population of rabbits exploded, causing an infestation that continues to cause millions of dollars’ worth of crop damage each year.
“What is interesting is that rabbits had already been introduced to Australia in 1788. Why did Austin’s rabbit release cause such a population explosion and not the earlier release?
Thanks to the recent study, scientists now have the answer.
Photo by Lance Reis on unsplash
“After sequencing the genomes of nearly 300 rabbits from Europe, South America, and Oceania, we found that all of them had a mix of feral and domestic DNA. This was not what we had expected to find — we expected that feral rabbits were domestic rabbits that have somehow relearned how to live in the wild. But our findings show us that these rabbits already had a portion of wild DNA helping them survive in nature.”
Andersson’s discovery explains why the 24 rabbits introduced to the Australian landscape in 1859 were so quick to adapt to living in the wild — they already possessed the right genetic traits that would help them thrive.
Rewilding Domestic Rabbits
Returning a species to the wild after centuries of domestication isn’t a simple process. Domestic rabbits have been bred by humans to be more docile and trusting than their wild counterparts. They are also often bred to have certain coat colors that humans find attractive — like all-black or all-white coats — that make them easier for predators to spot in the wild.
“During the rewilding process, natural selection removes many of these domestic traits because they are maladaptive — or unhelpful for survival — in the wild,” Andersson explains.
“But it’s not just coat colors that change. We also observed that many of the genetic variants removed during natural selection are related to behavior, like tameness. This brings back the wild flight instinct that is important for eluding predators.”
The entire process appears to depend on whether the rabbits already have wild genes in their DNA as a sort of foundation for the rewilding process.
“We hope that this study will help lawmakers understand the importance of preventing domestic animals from being released into the wild. This project has helped us understand not only how rabbits become feral but also how other species like pigs and cats can become feral nuisances.”
The study is a collaboration with the Research Center in Biodiversity and Genetic Resources (CIBIO), a Portuguese research organization.
Nature Ecology & Evolution Research Abstract
“Humans have moved domestic animals around the globe for thousands of years. These have occasionally established feral populations in nature, often with devastating ecological consequences. To understand how natural selection shapes re-adaptation into the wild, we investigated one of the most successful colonizers in history, the European rabbit. By sequencing the genomes of 297 rabbits across three continents, we show that introduced populations exhibit a mixed wild–domestic ancestry. We show that alleles that increased in frequency during domestication were preferentially selected against in novel natural environments. Interestingly, causative mutations for common domestication traits sometimes segregate at considerable frequencies if associated with less drastic phenotypes (for example, coat colour dilution), whereas mutations that are probably strongly maladaptive in nature are absent. Whereas natural selection largely targeted different genomic regions in each introduced population, some of the strongest signals of parallelism overlap genes associated with neuronal or brain function. This limited parallelism is probably explained by extensive standing genetic variation resulting from domestication together with the complex mixed ancestry of introduced populations. Our findings shed light on the selective and molecular mechanisms that enable domestic animals to re-adapt to the wild and provide important insights for the mitigation and management of invasive populations.”