Ok, many people have been asking about the taxonomy of ratsnakes. Notice I use the word ratsnake not rat snake. That is personal preference, it really does not matter which you use, both are generally considered correct.
First lets deal with the Russian study that said led to the internet confusion about the genus. It was this study (and if anyone has read it they can understand that it was a poorly done study) that led people to start using the genus Pantherophis. That is easily dispatched. Herpetological review in 2003 rejected this (Crother et al., 2003 Herp. Rev. 34: 196-203.) Further there has been no ruling by the International Committee for Zoological Nomenclature. Without a ruling from that body, any taxonomic change is a taxonomic suggestion only. Unfortunately, many people do not understand that. You must remember that 85% of all things published are found to be wrong in scientific literature within a decade. Do not take taxonomic suggestions seriously. Do not jump on the bandwagon too quickly. Many papers get published because someone is trying to get their name in the literature and they get things through by selecting journals with less rigorous review. The last farce was Burbrink's papers that used mitochondrial DNA to try to separate subspecies that are known to interbreed and produce fertile offspring in the wild as different species and to name a color morph of Elaphe guttata after is dead friend Slowinski. The slowinski corn snake is nothing of the kind. Living in Louisiana I have had the opportunity to go and examine numerous snakes of this morph and I have even seen animals freely interbreeding with Elaphe guttata when placed in cages with both morphs present. In fact the cage was about the size of a small room and had four of each kind in it. Interbreeding occurred freely as far as I and the owner could tell. I actually witnessed the act of breeding between the two morphs in the cage. Therefore I doubt the validity of the species. The resulting eggs were fertile and the offspring have gone on to breed with both morphs. Without a reason to separate the species, the morphs must be considered to be the same species. If they behave like a single species and there is gene flow, they must be the same species.
I could also go into the dangers of mitochondrial DNA, but that is a discussion for another time. Suffice it to say that mito DNA is bacterial in nature, freer to mutate and is a dangerous guide to deciding species. It is constructed like the DNA of a bacterium and even has bacterial type ribosomes that carry out the forming of protein from the instructions. It, like its bacterial ancestors (yes most cell biologists believe that mitochondria were bacteria at one time that became part of the eukaryotic cell) it lacks mutation correction machinery on the level of the eukaryotic nucleus and so it is more free to mutate. In nature if the nuclear DNA is similar enough, the sperm and egg of mating individuals can form fertile offspring. Thus this is a natural species. It behaves in nature like a species. The problem with all the taxonomy is that the natural species concept is ignored. Humans create delineations while nature works in a continuum. It really doesn't matter what percentage difference there is between the mitochondrial DNA of two morphs if their nuclear DNA allows them to behave like a single species in the wild.
I do not accept the slowinski corn snake nor the genus Pantherophis as valid. There is simply no reason to.