MISSOULA Until recently, little has been known about what genetic changes transform wild animals into domesticated ones. An international team of scientists, one of whom is a University of Montana assistant professor, has made a breakthrough by showing that genes controlling the development of the brain and the nervous system were particularly important for rabbit domestication.
The study was published Aug. 28 in Science and gives answers to many genetic questions. It is online at http://www.sciencemag.org/.
The domestication of animals and plants, a prerequisite for the development of agriculture, is one of the most important technological revolutions during human history. Domestication of animals started as early as 9,000 to 15,000 years ago and initially involved dogs, cattle, sheep, goats and pigs.
The rabbit was domesticated much later, about 1,400 years ago, at monasteries in southern France. It has been claimed that rabbits were domesticated because the Catholic Church had declared that young rabbits were not considered meat, but fish, and could therefore be eaten during Lent. When domestication occurred, the wild ancestor, the European rabbit, was confined to the Iberian Peninsula and southern France.
"The domestication of rabbits depended upon small genetic changes in many genes rather than more radical mutations in a few genes," explained Jeffrey Good, UM assistant professor and a co-author on the study. "This pattern contrasts with the large-effect genetic changes that are typically associated with striking differences in the size or appearance of diverse domestic dog breeds, for example. These results are exciting because they shed light on what types of genetic modifications are likely to be important during the early stages of domestication."
The scientists first sequenced the entire genome of one domestic rabbit to develop a reference genome assembly. Then, they resequenced entire genomes of domestic rabbits representing six different breeds and wild rabbits sampled from 14 different places across the Iberian Peninsula and southern France.
"No previous study on animal domestication has involved such a careful examination of genetic variation in the wild ancestral species," said Leif Andersson, a professor at Uppsala University, Swedish University of Agricultural Sciences and Texas A&M University. "This allowed us to pinpoint the genetic changes that have occurred during rabbit domestication." In contrast to domestic rabbits, wild rabbits have a very strong flight response because they are hunted by eagles, hawks, foxes and humans and therefore must be very alert and reactive to survive in the wild.
In fact, Charles Darwin wrote in "On the Origin of Species" that "no animal is more difficult to tame than the young of the wild rabbit; scarcely any animal is tamer than the young of the tame rabbit." Darwin used domestic animals as a proof-of-principle that it is possible to change phenotypes by selection.
The scientists involved in the current study have now been able to reveal the genetic basis for this remarkable change in behavior, and the study has given important new insights about the domestication process.
The study also revealed which genes have been altered during domestication. The researchers were struck by the strong enrichment of genes involved in the development of the brain and the nervous system, which are among the genes particularly targeted during domestication.
The study also shows that the wild rabbit is a highly polymorphic species that carries gene variants that were favorable during domestication, and that the accumulation of many small changes led to the inhibition of the strong flight response one of the most prominent phenotypic changes in the evolution of the domestic rabbit.
"We predict that a similar process has occurred in other domestic animals and that we will not find a few specific genes that were critical for domestication," Andersson said.
|Contact: Jeff Good|
The University of Montana