DNA Study Sheds Light on Evolution of Dog Breeds
Genetic material from 161 modern breeds helped a team of researchers at the National Human Genome Research Institute (NHGRI) of the National Institutes of Health assemble the most comprehensive evolutionary tree of dogs. The results are published in the journal Cell Reports .
Representatives from each of the 23 clades of breeds. Breeds and clades are listed for each picture from left to right, top to bottom: (A) Akita/Asian spitz; (B) Shih tzu/Asian toy; (C) Icelandic sheepdog/Nordic spitz; (D) Miniature schnauzer/schnauzer; (E) Pomeranian/small spitz; (F) Brussels griffon/toy spitz; (G) Puli/Hungarian; (H) Standard poodle/poodle; (I) Chihuahua/American toy; (J) Rat terrier/American terrier; (K) Miniature pinscher/pinscher; (L) Irish terrier/terrier; (M) German shepherd dog/New World; (N) Saluki/Mediterranean; (O) Basset hound/scent hound; (P) American cocker spaniel/spaniel; (Q) Golden retriever/retriever; (R) German shorthaired pointer/pointer setter; (S) Briard/continental herder; (T) Shetland sheepdog/UK rural; (U) Rottweiler/drover; (V) Saint Bernard/alpine; (W) English mastiff/European mastiff. Image credit: Parker et al , doi: 10.1016/j.celrep.2017.03.079.
The team, led by NHGRI dog geneticist Dr. Elaine Ostrander, examined genomic data from the largest and most diverse group of breeds studied to date, amassing a dataset of 1,346 dogs representing 161 breeds.
Included are populations with vastly different breed histories, originating from all continents except Antarctica, and sampled from North America, Europe, Africa, and Asia.
“There are nearly 400 modern domestic dog breeds with a unique histories and genetic profiles,” Dr. Ostrander and co-authors said.
“To track the genetic signatures of breed development, we have assembled the most diverse dataset of dog breeds.”
“Combining genetic distance, migration, and genome-wide haplotype sharing analyses, we uncover geographic patterns of development and independent origins of common traits.”
Most popular breeds in America are of European descent, but in the study, the authors found evidence that some breeds from Central and South America — such as the Peruvian Hairless Dog and the Xoloitzcuintle – are likely descended from the ‘New World Dog,’ an ancient canine sub-species that migrated across the Bering Strait with the ancestors of Native Americans.
Archaeologists have previously reported evidence that the New World Dog existed, but this work marks the first living evidence of them in modern breeds.
“What we noticed is that there are groups of American dogs that separated somewhat from the European breeds,” said NHGRI dog geneticist Dr. Heidi Parker, first author of the study.
“We’ve been looking for some kind of signature of the New World Dog, and these dogs have New World Dogs hidden in their genome.”
It’s unclear precisely which genes in modern hairless dogs are from Europe and which are from their New World ancestors, but Dr. Ostrander, Dr. Parker and their colleagues hope to explore that in future studies.
This evolutionary tree shows the relationships between dog breeds. Breeds that form unique clades supported by 100% of bootstraps are combined into triangles. For all other branches, a gold star indicates 90% or better, black star 70-89%, and silver star 50-69% bootstrap support. Breeds are listed on the perimeter of the circle. A small number of dogs do not cluster with the rest of their breed, indicated as follows: * cane paratore, + Peruvian hairless dog, # sloughi, @ country-of-origin salukis, and ˆ miniature xoloitzcuintle. Image credit: Parker et al , doi: 10.1016/j.celrep.2017.03.079.
Other results were more expected. For instance, many breeds of ‘gun dogs,’ such as Golden Retrievers and Irish Setters, can trace their origins to Victorian England, when new technologies, such as guns, opened up new roles on hunting expeditions.
Those dogs clustered closely together on the phylogenetic tree, as did the spaniel breeds.
Breeds from the Middle East, such as the Saluki, and from Asia, such as Chow Chows and Akitas, seem to have diverged well before the ‘Victorian Explosion’ in Europe and the United States.
Herding breeds, though largely European in origin, proved to be surprisingly diverse.
“When we were looking at herding breeds, we saw much more diversity, where there was a particular group of herding breeds that seemed to come out of the UK, a particular group that came out of northern Europe, and a different group that came out of southern Europe, which shows herding is not a recent thing,” Dr. Parker said.
“People were using dogs as workers thousands of years ago, not just hundreds of years ago.”
Different herding dogs use very different strategies to bring their flocks to heel, so in some ways, the phylogenetic data confirmed what many dog experts had previously suspected.
“What that also tells us is that herding dogs were developed not from a singular founder but in several different places and probably different times,” Dr. Ostrander said.