No, some morphs are mutated recessive genes, such as albino, anerythristic, melanistic, and a few others. Those are found in the wild and people breed to select those genes to produce the morphs in captivity. Some morphs are just natural variation or polymorphism. A "snow" is the result of combining two recessive genes which both get expressed in a single snake. That one would not likely occur in nature, but the two recessive traits needed to make them are both found in the wild. None of these morphs are produced by crossing species or subspecies. Like we were saying, crossbreeding garters is generally frowned upon.