|According to the AKC, this great Dane is a "mismark" due to being merle instead of harlequin (which is actually a merle underneath all the white). Merles and other mismarks are a very common product of breeding harlequin Danes due to the harlequin gene being lethal in the homozygous form. Harlequin x harlequin matings are especially dangerous due to the high likelihood of producing homozygous merles, who are very often blind and/or deaf.|
In practically every dog breed in the world, you have color standards. Any color that appears that does not fit with the usual standard is considered a "mismark" and thus "bad." Even in the breeds for which the standard says color does not matter, this is often not really the case. Why? In some cases, other aspects of the breed standard make such colors "undesirable." For example, if a standard does not allow yellow eyes, the brown or liver coloration would be considered undesirable since it always produces light, amber eyes. What is more often the case, however, is that the breeders have some sort of preference. Whether this is a preferred color for the entire breed or not, practically every dog breeder out there has their own views on what they think is attractive, and as such they will breed for some color in particular. Just look through their kennel. What diversity do you see? Probably not very much.
|This papillon is a "mismark"since there is white around its eyes|
|This poodle is a "mismark" due to its sable markings|
|Ebon is a "mismark" due to the red on his legs and face|
|This German shepherd is a "mismark" due to its (lack of) color|
|An adult male island deer in spring, showing the unusual phenotype seen in the population (if you look closely you can see the pedicle from which the antlers grow).|
So, my point is this: is a dog blue but should be black, but otherwise is what the breeder is looking for, why not breed from it? Each dog that is taken out of a closed population is more diversity lost. By reducing the number of traits that are considered "undesirable," it gives the potential to help keep genetic diversity up. If a closed registration system has any chance of working, this only makes sense. However, in so many cases the damage has already been done and it may be far too late to keep the registries closed. As such, carefully done out-crossing may be the only thing that can save many purebreds. That is, if people wish to maintain the breeds that are currently seen in the purebred dog world.