Okay, I've formed my opinion on whether Biewers are a separate breed from Yorkshire Terriers based on the information I currently have. It could change based on new research, so it isn't set in stone, but here it is:
Based on the results of breed purity analysis conducted by MARS Labs, I can only conclude that the 100 Biewers that were tested do indeed contain DNA from other breeds of dogs. And the PCA analyses conducted by MARS Labs indicate that these Biewers are fairly uniform, and cluster in their own group separate from Yorkshire Terriers. To me, that meets the definition of a separate breed, but ultimately it's the AKC and other registries who will have to make that decision.
How these other breeds got mixed in Yorkshire Terriers to create the Biewer Terrier is somewhat a mystery to me (perhaps falsified pedigree records in the distant past or "oops" matings, but I am not going to point fingers because those people are long gone and we have no real way of knowing), but the DNA evidence is there, and it is very strong. For me, the smoking gun is the piebald spotting gene (MITF gene) on chromosome 20. This isn't a simple random mutation that can spontaneously occur over and over, but appears to have originated once during the domestication of dogs, and been transferred to the breeds with piebald spotting by crossbreeding and selection. In the breeds analyzed so far, all piebald spotting genes carry a unique DNA insertion called a SINE in the upstream regulatory region of the MITF gene (the part of the DNA that controls the expression of the MITF gene--where and when the gene will be expressed during the dog's growth and development) as well as a separate length polymorphism (segment of DNA that can vary in length) in the upstream regulatory region. The chances against both changes occurring at once spontaneously in a single Yorkshire Terrier are astronomical. My conclusion is that the piebald spotting gene had to have been bred in from another breed of dog during the development of the Biewer Terrier. The way to resolve this question once and for all would be to completely sequence the upstream regulatory regions of the MITF gene in Biewers and see whether it indeed carries the SINE and the length polymorphism. If it does, then it's a done deal as far as I am concerned that the Biewer arose from breeding a Yorkshire Terrier with another breed and re-extracing the piebald color gene.
Since I am a believer in the conservation of genetic resources, my recommendation is that Biewers be bred only with other Biewers in order to preserve their unique characteristics, which go beyond color, but also include behavioral differences. If you keep crossing Biewers back to Yorkshire Terriers, you are going to lose these unique characteristics, and end up with something more like a Yorkshire Terrier, but yet will never quite be a Yorkshire Terrier.
Okay, I'm stepping down off my soapbox now. If you disagree, it's all good, but please be kind and don't shoot the messenger. Thanks! |