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BREED specifications for pure-bred/pedigree dogs are laid down by the organisations that register and judge dogs, such as the Kennel Club of the UK (KCUK) and the Kennel Union of South Africa (KUSA), as well as the umbrella body the Fédération Cynologique Internationale (FCI). Reproductive isolation between breeds results because animals can only be registered as a specific breed if they have five previous generations of ancestors registered as the same breed, creating a ‘breed barrier’ which promotes genetic differences among breeds. This genetic isolation in a population of UK dogs (Mellanby and others 2013) has been demonstrated previously. The lowest heterozygosities of around 0.5 were found for breeds such as the German shepherd dog, rottweiler and boxer dog, indicative of a reasonably high level of inbreeding. Labrador retrievers and border collies had heterozygosities of around 0.7, indicating greater genetic diversity. The Jack Russell terrier is not a registered breed with the KCUK. This group had a heterozygosity of close to 0.8 and maintained a high degree of genetic variability.
The authors were interested to assess whether dog breeds in another country had similar levels of genetic isolation. Three popular breeds were chosen, which showed differing heterozygosities in the UK: the German shepherd dog, the labrador retriever and the Jack Russell terrier (Mellanby and others 2013). Breed specifications for the labrador retriever were identical for the KCUK and the KUSA, whereas the specification for the German shepherd dog in South Africa is taken from the FCI criteria rather than the KCUK criteria which are very similar. The Jack Russell is not a KCUK-registered breed (Mellanby and others 2013) but is registered with the KUSA, conforming to the breed standard of the Australian National Kennel Council. Therefore, it might be expected to show …