Over 250,000 Border Collies have been registered with the ISDS since its founding over a century ago even though they didn’t really keep comprehensive stud books in earnest until the 1940s. Registrations have remained steady over the last few decades with 5,000 – 7,000 dogs being born and registered every year. This is the founding gene pool for all Border Collies worldwide and save for a dash of “local flavor” in the form of a Kelpie, English Shepherd, Beardie, pre-ISDS Border Collie, etc. thrown in, it represents the lion-share of global genetics for the breed.
Despite sizeable numbers of dogs in the UK, Europe, America, and Australia and New Zealand, and despite having a “founding” population of several hundred dogs, the current genetic information in the breed has been distilled down to just 8 individual genomes worth of information.
Teun van den Dool ran the entire published ISDS stud book through genetic analysis software and discovered this:
- There are 643 registered foundation dogs with genetic influence on the current population.
- 0.01% (25) of all registered dogs determine 75% of the genes in the current population.
- Effectively the genes of only 8 of the founder dogs determine the genes in the current population.
It seems that the current Border Collie population is dominated by a small number of dogs. Another way of looking at the gene base of a population is to define the foundation dogs (founders). These are the registered dogs with one or two unregistered parents. The unregistered parents could also be considered the founders but because they have no ISDS numbers it is not easy to find out which unregistered parents are equal for different registered pups. In that case the number of founders would be higher than in reality.
There are 3143 registered founders of which 1481 produced registered children. Only 643 of them have had influence on the pups born in the last five year.
A more detialed explanation of those 8 dogs:
This third algorithm gives EG, the effective number of different genomes from founders that are still present in the current population. It does so by simulating the random selection of a particular gene during the fathering of all dogs ever registered. After this simulation the genes in the current generation of Border Collies are counted. This simulation of the total Border Collie population is repeated many times (1000 in this case) and the average occurrences of the genes are calculated from the results. For the current ISDS population the effective number of founder genomes is EG=8.3. So effectively the genes of only 8.3 founder dogs are present in the current generation of approximately 25000 ISDS registered Border Collies. Amazing isn’t it?
Figure 4 shows how the different (effective) numbers of dogs have evolved over generations since the fifties. Before 1950 the pedigrees are incomplete and show a wild behavior starting at zero around 1900. Since 1980 the effective numbers are almost constant. Sometimes even a bit increasing due to ROM (Registered On Merit) dogs or dogs with otherwise unknown parents. So the main selection took place before 1980. Maybe not accidentally the last big reduction in genetic diversity (1965-1975) coincided with the rising star of Wiston Cap 31154.
A little extra explanation for those puzzled which those 8 ‘effective’ dogs are. They do not exist in reality, we cannot point at these 8 individual dogs. You should think of it as an amount of genes spread over all dogs. Many dogs have the same genes and only very few different genes are present in our dogs, only an equivalent of 8 dogs. That is what ‘effectively’ 8 dogs means.
Another way of looking at it is, suppose that we would have 8 founder dogs with differences in their chromosomes. We let them mate with each other randomly to produce a new generation of 25000 pups. This new generation will have the same genetic diversity as the current ISDS population. In this example we can point at the 8 effective dogs but in reality we cannot, the chromosomes have been selected over many generations from many dogs.
You might think ‘but Wiston Cap must be one of them’. Well, he surely caused a considerable reduction in the effective number of genomes but he did not add anything. He just caused a particular selection of chromosomes from its ancestors to become more dominant.
This analysis is an example of how current population numbers don’t tell the complete story of breed health. Regardless of current size, past bottle neck events mean that hundreds of thousands of Border Collies across the planet still only hold the genetic information of 8 individual genomes. It just might be the case that a small or even rare breed with only a few hundred members contains more unique genetic material than Border Collies do.
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