The Llewellin Setter and its Gene Pool.
The Llewellin Setter and its Gene Pool.
There is in excess of 500 documented canine genetic that fact alone emphasizes the importance of genetic diversity within the various breeds to prevent promoting deleterious alleles (genes). Most breeds of dogs including the Llewellin setter are heavily inbred which is most accurately measured by the percentage of homozygous loci (groups of matching genes).
The restricted gene flow associated with most modern breeds originates from several sources. In many cases, a limited number of founders were responsible for creating a breed. In some cases, other bottlenecks associated with shifts in breed popularity, the use of popular sires and even catastrophic world events has generated breeds with limited gene pools.
We know, for instance, that domestication was a major bottleneck. Molecular genetic data consistently support the origin of dogs from grey wolves. The origin now suggested is from Middle Eastern wolves. Once again the founding event may have developed over a long period of time with many individuals or the opposite, with a few habituating with early humans and spreading through migration and trade.
The development of individual dog breeds creates another genetic bottleneck. For example, the American population of basenjis, an ancient breed possibly originating in Egypt, is descended from two dogs brought from Africa in the 1940’s. Although this is an extreme example, almost all modern breeds were founded from a few individuals. In addition, most breeds have been around for relatively short periods of time and in many cases developed using popular sires. The use popular sires can be a prime source of dispersing recessive harmful alleles within a breed. In addition, dogs of the different breeds clearly display characteristic phenotypes such as morphologies (body shape, etc.), and behaviors from generations of inbreeding for these traits. The selection for breed traits without regard to susceptibilities to disease and maladies has caused serious problems in many modern dog breeds.
The establishment of breed clubs represents what is referred as “a breed barrier rule” and as a result each modern dog breed is now considered an isolated breeding population, defined by the assemblage of traits maintained under strong selection as previously mentioned. A factor that is important to genetic diversity and related to breed clubs is population size. An example is the popular Labrador with about 150,000 new dogs registered each year that creates a large diverse breed population, and because of this, more heterozygosis (more genetically diverse).
So, how do these factors just outlined, fit the historical development of the Llewellin setter? The Llewellins like most breeds, started with a few founding dogs and it is this genetic foundation that we still have in today’s setters. Mr. Llewellin’s dogs were a combination of Lavarack with the Duke-Rhoebe blood. These two foundation lines of the Llewellin Kennel differed so widely in characteristics that great variations have been recorded by observers both in England and America; variations that we still see today in the modern Llewellin setter. But does that mean a genetically diverse breed? Without extensive genome studies we cannot answer that question accurately. But, there are other events that would indicate that in general, it is not diverse. Both the small numbers in the breed and a major breed bottleneck in the later part of the twentieth century would lead us to this conclusion. For reasons that would only be speculation, a particular breeder in Arkansas came to dominate the breeding and sales of Llewellin setters, largely reducing the Llewellins population into a major bottleneck. And although his breeding practices and selection can be characterized as random, random selection in a small population leads to less genetic diversity as traits are lost through genetic drift. During the same time period, field setters were being bred specifically for competition by numerous major kennels.
The point is, it is more appropriate to look at genetic diversity in a breed as the number of distinct lines, not the genetic diversity of any individual dog and with the strong selection for desirable traits by many breeding kennels, the field English setter developed numerous genetically distinct lines. Not so with the Llewellin setter in America.
Our solution to a general lack of genetic diversity is to find superior Llewellins from distinctly different genetic lines by importing dogs from Belgian and Italy, and combining them with outstanding American Llewellins. This has lead to a substantial reduction in genetic maladies and a setter far superior in performance than what is a typical American Llewellin field dog.