Abstract
BackgroundDiscrete breed ideals are not restricted to delimiting dog breeds from another, but also are key drivers of subpopulation differentiation. As genetic differentiation due to population fragmentation results in increased rates of inbreeding and loss of genetic diversity, detecting and alleviating the reasons of population fragmentation can provide effective tools for the maintenance of healthy dog breeds.ResultsUsing a genome-wide SNP array, we detected genetic differentiation to subpopulations in six breeds, Belgian Shepherd, English Greyhound, Finnish Lapphund, Italian Greyhound, Labrador Retriever and Shetland Sheepdog, either due to geographical isolation or as a result of differential breeding strategies. The subpopulation differentiation was strongest in show dog lineages.ConclusionsBesides geographical differentiation caused by founder effect and lack of gene flow, selection on champion looks or restricted pedigrees is a strong driver of population fragmentation. Artificial barriers for gene flow between the different subpopulations should be recognized, their necessity evaluated critically and perhaps abolished in order to maintain genetic diversity within a breed. Subpopulation differentiation might also result in false positive signals in genome-wide association studies of different traits.Lay summaryPurebred dogs are, by definition, reproductively isolated from other breeds. However, similar isolation can also occur within a breed due to conflicting breeder ideals and geographic distances between the dog populations. We show here that both of these examples can contribute to breed division, with subsequent loss of genetic variation in the resulting breed lineages. Breeders should avoid creating unnecessary boundaries between breed lineages and facilitate the exchange of dogs between countries.
Highlights
Discrete breed ideals are not restricted to delimiting dog breeds from another, and are key drivers of subpopulation differentiation
We show here that both of these examples can contribute to breed division, with subsequent loss of genetic variation in the resulting breed lineages
We analyzed the genetic differentiation in Belgian Shepherd, English Greyhound, Italian Greyhound, Finnish Lapphund, Labrador Retriever and Shetland Sheepdog using multi-dimensional scaling (MDS) [15] and STRUCTURE [16] analysis of the genotypes of the 1319 Single nucleotide polymorphism (SNP)
Summary
Discrete breed ideals are not restricted to delimiting dog breeds from another, and are key drivers of subpopulation differentiation. The domestication process itself has caused genetic bottlenecks shaping dog development, the first dated to have occurred about 15, 000 years ago [1, 2]. While early domestication was characterized by adaptation to the mutualistic relationship with humans, different dietary conditions and geographical differentiation, the recent bottlenecks are much more dramatic and caused by goal-directed breeding, especially during the last two centuries. The idea of discrete, uniform and standardized dog breeds originates from the Victorian era and current breeding practices largely still reflect this thinking [3]. Competition brings prestige and some income from sales and stud fees for the owners, but more importantly forces the specification of ideal breed conformation
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