It is impossible to breed a blue rose or a cat with a bulldog shape. This is because breeding is limited by gene variations in the population.
What do breeders call this effect?
I guess this term is from medieval and/or handicraft breeders, not modern and hi-tech.
I am speaking not about principal impossibility but just about observable or tangible barrier. We can be sure that it is possible to turn dog into cat in billion years, but it is much harder than turn German Shepherd to Yorkshire Terrier, which is possible for hundreds of years.
So, there are are two main types of changes, ones take hundreds of years, others take hundreds of millions of years. Former require genetic recombination while latter require genetic mutation.
This barrier was felt by breeders in practice and caused some versions of anti-evolution beliefs.
I need to know how this barrier is named.