The Rabbit Rift
By all accounts, Pope Gregory I was quite the innovator. Along with his many liturgical accomplishments, he’s credited (somewhat apocryphally) with popularizing Gregorian chant, coining the phrase ‘bless you’ after someone sneezes, and perhaps, most unwittingly, creating one of the best experimental models for studying the evolution of domesticated animals.
As the story goes, around the year 600, Pope Gregory declared that baby rabbits, known as laurice, were in fact fish—thus allowing them to be eaten during lent. Thrilled with the news, monks in southern France welcomed a few unlucky wild rabbits inside their monastery walls. Over the next 1,400 years the two rabbit populations – one bred in captivity, the other left to multiply in the wild – went their separate evolutionary ways. Today, domesticated rabbits are a popular house-pet, research model, and food source, while their wild cousins still roam the grasslands of southern France.
This close evolutionary proximity presented a perfect opportunity for the geneticists and evolutionary biologists in the Broad Institute’s Vertebrate Genome Biology group.
“As the most recently domesticated animal, the rabbit allows us to study the early events of domestication,” said Kerstin Lindblad-Toh, scientific director of vertebrate genome biology at the Broad Institute. “In addition, since wild rabbits still live in Southern France we could compare the genomic changes between the domestic and corresponding ancestral population.”
In a paper published this week in Science, Lindblad-Toh, the members of her group and a team of international collaborators, shared the results of this first-ever genomic comparison of wild and domestic rabbits, and their findings suggest that the genetic mechanism of domestication may be more complex than initially thought.
The common assumption has long been that there must be a handful of genetic changes that led to domestication. But rather than implicating one or two genes, the study, which compared the genomes of six domestic breeds and 14 different wild rabbit populations, showed evidence of numerous subtle genetic shifts.
“By measuring precise allele frequency differences between tame and wild rabbits, we were able to find that thousands of brain genes have impacted rabbit domestication in different combinations,” said Lindblad-Toh, who also serves as a professor in comparative genomics at Uppsala University, and co-director of the Science for Life Laboratory Sweden. Based on this finding, the paper proposes that no single genetic change is either necessary or sufficient for domestication, and that the process is the result of an accumulation of many mutations of small effect.
“In some weird way, domestication resembles a complex disease like diabetes, where there are a whole bunch of changes, but not everyone has the same arrangement,” said Broad research scientist Jessica Alföldi, and co-author of the paper.
“Studies like this help us understand evolution on the molecular level,” said Alföldi. “We domesticated the rabbit to make it more convenient for us— and now we know exactly what happened to the rabbit genome in that process.”
Researchers from the Broad Institute who contributed to this study include Federica Di Palma, Jessica Alföldi, Jason Turner-Maier, Jean L. Chang, David Heiman, Jeremy Johnson, Sarah Young, Eric S. Lander, and Kerstin Lindblad-Toh.
Carneiro, Miguel et al. Rabbit genome analysis reveals a polygenic basis for phenotypic change during domestication. Science, DOI: 10.1126/science.1253714