My thoughts are that there are a couple of possible reasons why size varience continues to be an issue.
One is the misconception among some breeders that if you have a small bitch and breed her to a dog on the upper limits of acceptable size then you will get puppies which are correct. Which only gives usually a mix of more big and small ones and the occasional right for size.
Second is that in the past, the larger bitches were kept for whelping duties and their correct sized sisters did the showing. When people had larger kennels of dogs (and more money!) this was not a problem for them. Incidentally I breed dwarf rabbits and almost invariably we breed from the larger, coarser females rather than the show sized ones as the larger ones make much better mothers and don't have birthing issues experienced with smaller does. This does produce some variation in size but it is much less marked than seen in shelties.
As far as I know, size is not determined by one gene but by a whole lot all interacting together. It is certainly strange that such significant variations in size are seen after so many generations away from the collie outcross and with the vast majority of breeders only breeding from dogs which fall mid way between the two extremes.
It is also interesting that there appears to be a lot of variation in 'substance' in the breed. Using my own two dogs as examples, Revel has good bone and substance without being coarse. Yogi is within an inch the same size yet has much finer bone and is overall a less substantial dog.
One is the misconception among some breeders that if you have a small bitch and breed her to a dog on the upper limits of acceptable size then you will get puppies which are correct. Which only gives usually a mix of more big and small ones and the occasional right for size.
Second is that in the past, the larger bitches were kept for whelping duties and their correct sized sisters did the showing. When people had larger kennels of dogs (and more money!) this was not a problem for them. Incidentally I breed dwarf rabbits and almost invariably we breed from the larger, coarser females rather than the show sized ones as the larger ones make much better mothers and don't have birthing issues experienced with smaller does. This does produce some variation in size but it is much less marked than seen in shelties.
As far as I know, size is not determined by one gene but by a whole lot all interacting together. It is certainly strange that such significant variations in size are seen after so many generations away from the collie outcross and with the vast majority of breeders only breeding from dogs which fall mid way between the two extremes.
It is also interesting that there appears to be a lot of variation in 'substance' in the breed. Using my own two dogs as examples, Revel has good bone and substance without being coarse. Yogi is within an inch the same size yet has much finer bone and is overall a less substantial dog.
Most people know Savvy (owned by Barbara Bicksler) from agility before they ever meet Evie. Then they see Evie and say "that is Savvy's littermate?" Evie is only an inch taller than Savvy, but is 7 pounds heavier.