Dogs can be easily distinguished by variations in the patterns of their coat colors, which most commonly include black, brown, yellow, and white. In a new study from UC Davis, experts have had a breakthrough while studying a subset of dog color patterns.
The research suggests that one particular dog color pattern emerged two million years ago, long before dogs were domesticated.
The study pinpointed five distinctive dog color patterns that are produced by the agouti signaling protein (ASIP) gene. These five patterns can be found in hundreds of dog breeds and hundreds of millions of dogs around the world.
The international team of researchers discovered that the genetic combination which produces the coat pattern “dominant yellow,” or DY, is shared with Arctic white wolves. A genetic analysis revealed that DY originated in an extinct canid that diverged from gray wolves more than two million years ago.
Study co-first author Professor Danika Bannasch is the Maxine Adler Endowed Chair in Genetics at the University of California Davis School of Veterinary Medicine.
“While we think about all this variation in coat color among dogs, some of it happened long before ‘dogs’ were dogs,” said Professor Bannasch. “The genetics turn out to be a lot more interesting because they tell us something about canid evolution.”
The experts speculate that lighter coat colors would have been advantageous to a canid living in an Arctic environment. Natural selection would have allowed the coat pattern to persist in the population that eventually gave rise to dogs and wolves, explained the researchers.
“We were initially surprised to discover that white wolves and yellow dogs have an almost identical ASIP DNA configuration,” said study co-first author Chris Kaelin of the HudsonAlpha Institute for Biotechnology.
“But we were even more surprised when it turned out that a specific DNA configuration is more than two million years old, prior to the emergence of modern wolves as a species.”
Wolves and dogs make two different types of pigments – a black one called eumelanin and a yellow one called pheomelanin. The precisely regulated production of these two pigments leads to different dog color patterns. Yellow is controlled by the agouti signaling protein, which is produced by the ASIP gene.
The experts found that no single genetic mutation was responsible for the five major color patterns. The mutations occur in two areas of the ASIP gene to produce the various patterns.
Professor Bannasch and colleagues named the phenotypes: dominant yellow, shaded yellow, agouti, black saddle, and black back.
Based on genetics, the team set out to identify the origin of the dog color patterns. While the dominant yellow haplotype has been around for two million years, the black back pattern was identified in a dog sample that was 9,500 years old.
The study is published in the journal Nature Ecology & Evolution.
By Chrissy Sexton, Earth.com Staff Writer