Breeds are groups of animals bred for specific traits &/or mutations. Phenotype can evolve over hundreds, & thousands of years, as a result of the characteristics which prove advantageous in that environment. Genes swapped with animals of the same species, developing in different locations, under different selection pressures, influence each others development, & offer variety within the one grouping of animals.
This is a more species like means of evolution - dogs working alongside nomadic people are a good example.
Separating breeds by way of closing their gene pools is a more recent phenomenon, inspired largely by the eugenics movement.
In the reptile hobby, we often maintain we're working with 'species', not 'breeds', but selectively breeding anything can be described as breed development, by separating animals based on colour, & pattern we are edging towards the eugenics paradigm.