Tracking 150 years of strong artificial selection using historical dog genomes

• Applicant: Professor Laurent Frantz, Ph.D.
• Subject Area: Animal Breeding, Animal Nutrition, Animal Husbandry ; Evolution, Anthropology
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 524207393

The human penchant for novelty is exemplified by the tremendous diversity in sizes, shapes, and colors of dogs. The selection pressures underlying this disparity accelerated dramatically with the advent of competitive dog shows in the middle of the 19th century. As a result, breed dogs now possess more cranial shape and size variation than observed across the entire order Carnivora. Selective breeding often has negative consequences for the health and welfare of domestic populations. In fact, nearly 1,000 heritable disorders have been characterized in purebred dogs, many more than in mixed-breed and free-ranging dogs. The combined impact of the increased frequency of genetic disorders has led to dramatic reductions in the lifespan of purebred dogs compared to mixed-breed dogs (~1.2 years on average).For example, by selecting for specific alleles underlying a trait of interest, breeders may also inadvertently select alleles that are deleterious (harmful) through a process known as genetic hitchhiking. Breeding also leads to selective sweeps in the genome, which reduce genetic diversity, and increases the likelihood that deleterious recessive alleles are expressed as homozygous. What remains unknown is whether the largest impact on the decline in genetic diversity and increased mutational load in purebred dogs was the result of breed formation, the establishment of a breed from an unknown number of individuals in the 19th century, or the subsequent ~150 years of “improvements”. In other words, we do not know whether the genetic-related health consequences observed in modern breed dogs resulted primarily from the establishment of breeds from a small number of highly related individuals, or the later application of strong artificial selection for specific traits.Directly addressing these questions requires historical data including pedigree records and historical genomes. Here, we propose to firstly generate high quality ancient genomes from historical pedigree dogs (from 1840s to 2000s). We will then contrast these historic genomes with previously generated ancient and modern dog genomes, which will allow us to track microevolutionary processes in multiple dog breeds along a temporal continuum. Aside from addressing fundamental evolutionary questions about the nature and consequence of artificial selection, our results will also provide a robust understanding of the long-term health consequences of strong, directed, breeding. This has implications for veterinary medicine, ensuring sustainable breeding practices (by kennel clubs), as well as for our basic understanding of disease in dogs, which are used as a model for human disorders (e.g. retinal degeneration, narcolepsy, and obsessive compulsive disorder).

• DFG Programme: Research Grants
• Co-Investigator: Professor Dr. Joris Peters