Why I Find the "Mismark" Concept Ridiculous

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

Now, why do I think these views are ridiculous? Colors really shouldn't matter one iota. It all comes down to genetic diversity, and how selective breeding plays an effect on that diversity. Any form of selection narrows the gene pool, even if the breeder claims that it is to "preserve type." There will always be variation in a litter, and as such only a few will be bred from when there is a narrow type that is being bred for. Adding color as a variable will only cause there to be more dogs seen as "undesirable," and thus fewer dogs bred from and less genetic diversity. Why does it matter if a Labrador has tan points? Or if a great Dane is brindle with white markings? If a German shepherd is blue? Has white markings? If a Cavalier is black and tan with a large white patch on its chest? It is still a Lab, or a Dane, a GSD, or a Cavie. It is also an extremely common practice to breed based on a particular "color class" in breeds that do have very strict color standards and breeding certain pairs will be guaranteed to produce "undesirable" offspring. This basically produces breeds within breeds and as such further isolates a breed from not just other breeds, but in fact from itself.

This poodle is a "mismark" due to its sable markings

The purebred dog world is one of closed registries, which has led to countless issues associated with the health of the breeds. It's basic population genetics. Inbreeding leads to increased homozygosity in each successive generation, which causes a decrease in the overall health of the population. Despite what some breeders may say, the purebred dog world is one of heavy inbreeding. The story of the founding on a breed is generally almost identical to that of any other breed. Breeder likes dog type A and wants to continue its line. But, there are only five dogs of that type. So, the breeder breeds those five together to produce a new purebred dog. In other cases, a breeder sets out to create a particular type, taking a dog from here or a dog from there with certain traits they want. However, it may take several generations of specific inbreeding to get those desired traits to "stick" in the desired combination. The more traits, the more inbreeding that is necessary. Eventually, there may be hundreds of thousands of that particular breed. However, generation after generation, that heavy inbreeding does not just go away no matter how big the population gets and how much "out-crossing" that is done to different breeding populations within the breed. Any further inbreeding only compounds the issue, narrowing the gene pool with each successive incident. Line breeding (breeding to close relatives) and popular sires (the extreme excessive use of a dog that wins lots of awards) are just more complicated terms for inbreeding and again narrow the gene pool more and more. It's no wonder that so many breeds have strange genetic issues that often are seen in no other breed.

Ebon is a "mismark" due to the red on his legs and face

A further issue with the "mismark" is if a undesirable color occurs in enough frequency, or if a new color suddenly crops up in a breed, there will always be those who don't see why the color is "bad." This is my view, but their response is one that I disapprove of. Most often, the color is inherited recessively, and it is not uncommon for the color to become a novelty and become desirable to certain people. This leads to inbreeding to make the color more common. Inbreeding is the only way to really guarantee the reappearance of such a color, and as such it is common for father-daughter, mother-son, and brother-sister matings to be the first direction these breeders go. If they like the color enough, they either try to change the breed standard (which rarely ever ends up working) or they go and create their own breed. This has happened on multiple occasions, including twice in the German shepherd alone (with the white shepherd and panda shapherd). By taking that stock away from its original breed and isolating the breeding population it leads to greater lack of genetic diversity. This negatively effects the source breed, but is even worse for the breed that has been newly created.

This German shepherd is a "mismark" due to its (lack of) color

The foundation of a new breed of any domestic animal is almost identical to the founder effect seen in wild populations of animals and other living things. The founder effect is commonly seen in island populations. Islands tend to have less species diversity than what is seen on the local mainland. Why? It's difficult to cross a body of water unless the species is specifically designed to be semi-aquatic, and few species are of this type. So, only a few members of a few species will make it and start to populate the island. This leads to inbreeding, and greatly reduced genetic diversity. This is why island populations can exhibit strange features or behaviors. In a local example, I visited a private island several years ago that had no bridge connecting the island to the mainland. Since there was no highway for migration to and from the island, the populations there had been isolated for quite some time. The deer there were strange: small, squat, and basically unafraid of anything. There were no predators on the island, except for some unusually small feral pigs, so the deer were used to not having to worry for their lives. When comparing them to the deer on the mainland, the difference is quite remarkable. They are big, rather lightly built, and flighty. The deer also had a somewhat low reproductive rate, as I found out from those who frequented the island. This is a classic sign of an unhealthy population. The introduction of a few deer from the mainland would help with the health of the population. This is quite relevant to the healthy upkeep of any population, and purebred dogs, if they are to be maintained, must be approached like any population that we do not wish to have die out. A potential for input of new genes is cherished in the world of endangered and threatened species, so why not in the domestic animals that we love so much?

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.