I'll take a stab at it. It's a long, long story, so I'll try to be as brief as I can without being inaccurate. The piebald gene that gives Biewers and Parti Yorkies their distinct white patches did not originate spontaneously in the Yorkshire Terrier (as proven by DNA sequencing of the piebald gene)--it was bred in from another breed at some time in the past, and since it happened so long ago, there's no sure way of telling when and how. The Biewer lines, and at least some of the Parti lines, trace back to Stream Glen Kennels, so perhaps there is a common link there.
Parti lines have been kept close to the Yorkshire Terrier standard, and some of them have been maintained by crossing back into Yorkshire Terrier lines, so the AKC considers them to be a non-standard color Yorkshire Terrier, but a Yorkshire Terrier nonetheless.
Biewers, on the other hand, have generally been bred with other Biewers, and so their DNA has diverged enough from Yorkshire Terriers for them to be considered a separate breed. They can be distinguished from Yorkshire Terriers by DNA testing, and they were just recognized by the AKC's Foundation Stock Service as an emerging breed.
The Biewer controversy is this: Not all Biewer groups have been involved in Wisdom Panel DNA testing programs, and not all Biewer groups use the BTRA registry that was just accepted by the AKC's FSS program. The hope is that as more Biewers are tested, more will be found that conform to BTRA standards and receive acceptance into the AKC FSS program. That is the optimist in me speaking. The Biewers that have been bred by crossing into Yorkshire Terrier lines will probably not fare so well, and will probably continue to remain outside the AKC. |