July 3, 2020

Study Finds Variation in Breeding Practices and Geographic Isolation are Leading to Loss of Genetic Diversity within Dog Breed Lineages

Wisdom Health Genetics, makers of the WISDOM PANEL dog DNA tests, announced this week the publication in Canine Medicine and Genetics of a study conducted in collaboration with the University of Eastern Finland. The study, Variation in breeding practices and geographic isolation drive subpopulation differentiation, contributing to the loss of genetic diversity within dog breed lineages, describes genetic subpopulation differentiation and related loss of genetic diversity discovered in six dog breeds and advises breeders to take better care in supporting genetic diversity when breeding for certain desired traits.

Researchers examined the six popular dog breeds – the Belgian Shepherd, English Greyhound, Finnish Lapphund, Italian Greyhound, Labrador Retriever and Shetland Sheepdog – based on differential breeding strategies such as breeding for characteristics desired in ‘sporting’ compared to ‘show’ lines and geography using genotype analysis, finding that each of the breeds showed subpopulation differentiation contributing to a lack of genetic diversity.

For the Italian Greyhound and Shetland Sheepdog, the differentiation could be attributed to the founder effect – or the reduction in genetic diversity caused when a population descends from a small number of ‘founding’ ancestors, combined with geographical isolation based on continent. Breeder preferences accounted for the genetic structure of the remaining four breeds: the English Greyhound and Labrador Retriever breed structures were selected for either show, sport or working lineages. Analysis of the Belgian Shepherd breed structure shed light on the genetic relationships between different sub varieties of the breed; analysis of the Finnish Lapphund revealed a relatively recent, unexpected split within that subpopulation due to breeder preference.

“These findings are yet another example of how the genetic data generated during our commercial testing at Wisdom Health Genetics can be used to gain insight into the population structure and diversity levels of breeds and their subpopulations,” said Jonas Donner, Discovery Manager at Wisdom Health Genetics.

Though breed differentiation can serve important purposes, selection must be done critically and carefully to maintain healthy genetic diversity and increase gene flow between isolated populations.

“Breeding dogs to fulfill specific breed ideals, by definition, will result in a loss of variation over time; this differentiation is not generally negative. However, due to their size, many small breed populations are in danger of suffering from the accumulated effects of inbreeding depression over the generations,” said study co-author Jaakko Pohjoismäki, senior researcher in genetics at the University of Eastern Finland. “Breed organizations should be more proactive in mixing the dogs between specialized lineages or closely related breeds to prevent deleterious effects of inbreeding depression.”

It is essential to maintain a balance between preserving diversity within the breeds when selecting for desired characteristics; to continue responsible breeding, genetic diversity and selecting for positive health traits are central to keeping a population healthy.

“The results of this study highlight the importance of careful balancing between selection for desired traits and health and avoiding loss of genetic diversity,” said Rebecca Chodroff Foran, R&D Director at Wisdom Health Genetics. “Through our research, we aim to improve the lives of pets everywhere and identifying opportunities to maintain genetic diversity will ultimately help create and support healthier populations.”

Based on the observed loss of genetic diversity in subpopulations of the six breeds studied, the researchers recommend that breeders take steps to encourage genetic diversity, facilitating exchange of dogs across geographical borders and avoiding unnecessary artificial boundaries between lineages.

Subscribe to Pet Insight