In a 20-year study, researchers from the National Human Genome Research Institute in Bethesda, Maryland, rendered a digital map that shows the genetic relationships between each known dog breed.

The objective was to determine how the different dog breeds developed through time, resulting in a family tree that puts in coherent terms the evolution of clades and breeds.

Image credit: Pets4Homes
Image credit: Pets4Homes

This is the first study of its kind, as the period from when dogs were first domesticated up to today has been a mystery so far when it comes to their genotypes.

A map of all dog breeds

To draw the map, researchers used data of 1,346 dogs, among which they could classify 16 different breeds. The dog genome could be differentiated by analyzing 150,000 individual parts, which allowed researchers led by Elaine Ostrander and Heidi Parker to associate each breed with another. They also used publicly available data from 305 dogs whose genotypes were analyzed using the same procedures.

For tens of thousands of years, humankind has domesticated dogs for performing different tasks, such as hunting, herding, keeping out intruders, and many other duties. Today, experts are aware of nearly 400 different dog breeds, all of which have their own unique set of skills and character.

Most of the breeds were put in one of the 29 larger groups known as clades, which allowed researchers to put dogs with similar qualities next to each other. Dogs have been bred for agility, gathering, strength, and more. For example, collies and sheepdogs were put in the same clade, while spaniels and retrievers were put into another. Each clade included 2 to 16 breeds, and they account for 78 percent of the breeds present in the dataset.

It was revealed that different breeds share the DNA of dogs from different clades. This will allow veterinarians find the origin of genetic diseases, as they are often left without explanation and being credited solely to the dog breed’s origins.

Researchers note that the pug was confirmed to be closely related to the European toy breed, the Brussels Griffon. This is because the pug was imported from Asia, and then it was used to develop other small breeds, as previous research efforts have theorized it.

It also appears that most of the “New World” dogs, which are the dog breeds found in the Americas before the colony, were replaced through contact with European breeds and Asian migrations. Because migrants brought livestock with them, they also brought their herding dogs. Most of the European breeds’ genes were stronger than those of New World dogs, resulting in cross breeds with improved skills for herding. Most of the new breeds developed in America were the result of crossing New World dogs with European and Asian dogs.

Furthermore, the study shows that the environment in which the dog lived also contributed to its genotype:

“We observe further evidence of the role geography plays in the distribution of breeds within the clades. For instance, both the UK Rural and the Mediterranean clades include both sighthound and working dog breeds, two highly divergent groups in terms of physical and behavioral phenotype,” reads the research.

Source: Cell