Reptile & Amphibian Forums

A few of the readers of this forum have been talking about crossing different subspecies of obsoletus. Most of the justifications for doing such crosses were along the lines of wanting to see what they would look like. Since I have seen pictures of the crosses in question, I personally see no justification for producing such animals. The offspring of such crosses don’t seem to sell very well, and I am concerned that they will end up in the wild where they don’t belong.

Dwight Good made the point that obsoleta have been redefined into three species defined strictly by their geographic range and not by their coloring. This is a very good point that Mr. Good makes. If this system becomes accepted, we will have to know where the snake's wild origins are from to tell if our Black Rat is an intergrade or a purebred alleghaniensis.

The evidence for this reclassification comes out of research that was published in “Evolution” back in May of 2000. The paper was submitted for publication by Frank Burbrink, Lawson & Slowinski, and the title of this paper is “MITOCHONDRIAL DNA PHYLOGEOGRAPHY OF THE POLYTYPIC NORTH AMERICAN RAT SNAKE (ELAPHE OBSOLETA): A CRITIQUE OF THE SUBSPECIES CONCEPT”. (You can find a copy of it on the web.)Under this system, you can forget about the genus Pantherophus and go back to Elaphe.

The classification of these snakes is still being debated. I note that most of the people contributing in this forum refer to the obsoleta subspecies as being members of the genus Pantherophus and not Elaphe. Few use new system, i.e.: Elaphe alleghaniensis etc. to label their snakes. I will also point out that most of the scientific papers that I have seen do not use this new system either.

This system is based of evidence found in the mtDNA of these snakes, and this type of evidence for classification is being debated in the scientific community at this time. In fact there are many papers both pro and con dealing with the subject and it is not a “done deal.”

In no way am I trying to predict how this debate will turn out. What I am arguing for is caution. Using Burbrink’s evidence to justify the production intergrades that no one seems to want is not a good idea. The truth is that many unwanted animals end up released into the wild. This is a form of genetic pollution. I don’t think that those of us who love these snakes want to do anything that could injure wild populations. Since there is no market for such snakes, they should not be produced for the sake of someone’s curiosity. Besides, there are plenty of pictures of what you get when you cross these snakes. There is no good reason at this time to do so again.

>>The classification of these snakes is still being debated. I note that most of the people contributing in this forum refer to the obsoleta subspecies as being members of the genus Pantherophus and not Elaphe. Few use new system, i.e.: Elaphe alleghaniensis etc. to label their snakes. I will also point out that most of the scientific papers that I have seen do not use this new system either.
>>

Not to argue with you, I agree with much of what you said, but I would like to clarify some of the taxonomy.

In 2000 Burbrink reclassed the Elaphe obsoleta by creating several new species from this one species. However, the genus Pantherophis was resurrected in 2002 when Utiger et al. published their findings on the whole Elaphe genus, and there were eight other new genera. The type of taxonomy proposed by Burbrink is highly contested and not accepted by many as far as I know. The taxonomy by Utiger et al. is based on the closeness of the Lampropeltini, which Pantherophis is a part of, and its distance from the Old World ratsnakes (Elaphe). Pantherophis is well accepted, imho, and that is why it is being used, and used correctly, imho. Some people might be using Burbrink's "obsoletus" species, but I think most are not. If they are, it should be Pantherophis obsoletus, P. alleghaniensis, etc.

Thanks for listening....TC.

Some people might be using Burbrink's "obsoletus" species, but I think most are not. If they are, it should be Pantherophis obsoletus, P. alleghaniensis, etc.

I don't recall that Burbrink ever used "obsoletus." Do you have a citation? From what I've read he proposed the names E. obsoleta, E. spiloides, and E. alleghaniensis.

Obsoletus would be the correct usage if one adopts the Pantherophis name.

Later,
dg

>>Some people might be using Burbrink's "obsoletus" species, but I think most are not. If they are, it should be Pantherophis obsoletus, P. alleghaniensis, etc.
>>
>>I don't recall that Burbrink ever used "obsoletus." Do you have a citation? From what I've read he proposed the names E. obsoleta, E. spiloides, and E. alleghaniensis.
>>
>>Obsoletus would be the correct usage if one adopts the Pantherophis name.
>>
>>Later,
>>dg

Hi, Dwight. That is correct. I meant if you used Pantherophis. If you ignore Utiger, et al, then it would be Elaphe obsoleta, etc. I didn't mean that Burbrink used Pantherophis.

Cheers...Terry

Dwight Good made the point that obsoleta have been redefined into three species defined strictly by their geographic range and not by their coloring. This is a very good point that Mr. Good makes. If this system becomes accepted, we will have to know where the snake's wild origins are from to tell if our Black Rat is an intergrade or a purebred alleghaniensis.

I just wanted to clarify to everyone that my post below in reference to the Burbrink study was totally sarcastic. I don't care if the guy (Burbrink) is a molecular biologist (or whatever) I simply don't agree that a black rat snake from CT is the same genetically as an everglades rat snake from south FL!! BUNK is a word that comes to mind inside my pea sized brain.

After re-reading my post, it appeared that I might actually be agreeing the the split proposed by Burbrink. NOPE!!

Later,
dg

heh, I was wondering there for a sec

Hello Dwight,

I perfectly understand your reaction to Burbrink's reclassification of Pantherophis obsoletus into 3 separate species. I used to react similarly. Used to, because since then I've looked to (hundreds of) pictures and live specimens of known locality in a very different way. By ignoring colors and focusing on morphometrics, this classification didn't seem that far fetched anymore. A nice example are the Black Ratsnake pictures in 'A monograph of the snakes of the genus Elaphe Fitzinger' By Klaus-Dieter Schultz. All 3 of Burbrink's new ratsnake species are represented here as Black Ratsnakes. Just compare these pictures with those of the other subspecies of the good old polytypical P. obsoletus, and tell me if it doesn't make you wonder?

However, I still think Pantherophis obsoletus shouldn't be split into 3 separate species. The differences in mitochondrial DNA could very well be secondary in nature, as a result of the species' postglacial distribution and the emergence of natural geneflow barriers. Splitting the species into 3 separate taxa the way Burbrink et al intend to, may therefore lead to 3 paraphyletic taxa. Not a good idea, phylogenetically speaking. But I could be wrong about this as well.

Greetings,

Herman Bronsgeest.

>>Hello Dwight,
>>
>>I perfectly understand your reaction to Burbrink's reclassification of Pantherophis obsoletus into 3 separate species. I used to react similarly. Used to, because since then I've looked to (hundreds of) pictures and live specimens of known locality in a very different way. By ignoring colors and focusing on morphometrics, this classification didn't seem that far fetched anymore. A nice example are the Black Ratsnake pictures in 'A monograph of the snakes of the genus Elaphe Fitzinger' By Klaus-Dieter Schultz. All 3 of Burbrink's new ratsnake species are represented here as Black Ratsnakes. Just compare these pictures with those of the other subspecies of the good old polytypical P. obsoletus, and tell me if it doesn't make you wonder?
>>
>>However, I still think Pantherophis obsoletus shouldn't be split into 3 separate species. The differences in mitochondrial DNA could very well be secondary in nature, as a result of the species' postglacial distribution and the emergence of natural geneflow barriers. Splitting the species into 3 separate taxa the way Burbrink et al intend to, may therefore lead to 3 paraphyletic taxa. Not a good idea, phylogenetically speaking. But I could be wrong about this as well.
>>
>>Greetings,
>>
>>Herman Bronsgeest.

Herman, I know you didn't post to me, but I'd like to make a couple comments about the taxonomy anyway in case noone else answers.

I believe Burbrink said the gene flow barriers were the Mississippi R. and the Appalachian Mtns, but I'd have to see the paper again to be positive on that. I just can't see those landforms as barriers, or that there's enough of a difference from West to East to name three different species. Are we to believe P. g. emoryi and P. g. guttata aren't different enough to warrant species status, but P. obsoletus is, enough to warrant three different species. If anything I would think the Everglades rat is more different than any black rat, but then hobbyists are just seeing the snakes superficially, and not looking at the genes. I don't think the taxonomists care much what laymen like us think either. On the other hand we can think whatever we want, and for the time being, until there's a better argument, I'm going to consider obsoletus all one species.

PS: Maybe we should officially get a critique going and invite the whole forum to participate and see where everyone stands on this

Cheers....TC.

Hello Terry,

Like I said before, I still believe that the current taxonomical classification of Pantherophis obsoletus as a polytypical species should be maintained. However, Burbrink et al did make some very plausible arguments and these should be considered accordingly. If they turn out to be wright about this, this could mean that hobbyists who value the propagation op purebred Black Ratsnakes actually are breeding hybrids in most cases. I can perfectly understand that they would have a problem with that, so would I, but that doesn't change anything. For me it's hard to tell wether or not geological elements such as the Mississippi and Apalochicola Rivers or the Appallachian Mountains may serve as geneflow barriers, but it seems that these elements actually do coincide with the patterns in mitochondrial DNA as detected by Burbrink et al.

Burbrink et al also argue for P. emoryi and P. slowinskii as species separate from P. guttatus. Recently, P. vulpinus and P. gloydi have also been separated. The division of P. obsoletus into 3 separate species does not disagree with this pattern.

Greetings,

Herman Bronsgeest.

I must point out that there are also some very good arguments why the arguments like those of Burbrink et al and others who are using mtDNA evidence to separate species do not work.

>>I must point out that there are also some very good arguments why the arguments like those of Burbrink et al and others who are using mtDNA evidence to separate species do not work.

Thanks, Frank. Feel free to jump in. Do you happen to have a copy of Burbrink's paper?

Terry

Greetings again, Herman.

Next time I find a black rat I'm going to get my dna quick test kit out and find out which species it is...LOL! Couldn't resist. I hear what you're saying, but how can it make a difference to breeders when you can't tell the difference bt. different black rats?

I know Burbrink was also the one who proposed that Kisatchie Corns be split to the new sp., Elaphe slowinskii. This is one of the reasons I think he lacks credibility in the herping community. These corns are inbetween regular corns, P. g. guttatus, on the east, and Southwestern Ratsnakes, P. g. meahlmorum, and Emoryi's Rats, P. g. emoryi, to the west. They intergrade with the other subspecies at least a little, I think. Burbrink, et al., may be advocating for full species of E. emoryi, E. slowinskii, and E. guttata, but this hasn't been accepted by even the academic community, yet. I accept Slowinski's Corn as a subspecies, P. g. slowinskii, but am not ready to accept it as full species w/o more evidence.

While the trend of splitting out species goes along with what CNAH is doing, each case must be looked at individually as to its own merits. What evidence or data has been given for splitting emoryi and guttata in the corn snake group? With vulpina and gloydi in the fox snake group, I can see more acceptance, presumably because there is a greater separation bt. their ranges. At first I didn't think there was enough difference bt. vulpina and gloydi, but there is a fair distance bt. their ranges, and I'll accept it if it is accepted by academia. With the obsoletus group there just doesn't seem to be enough evidence. Who's to say the little bit of genetic variation is reason enough to split a species when nothing else points that way. What ever happened to the idea that unlike species didn't reproduce viable offspring together? Arrrrgh!

TC

Don't get me wrong Terry, my feelings regarding this issue are exactly the same as yours. I just find the arguments provided by Burbrink et al interesting to argue about, but I certainly do not take their conclusions for granted. The same arguments could be used to split Homo sapiens into an almost infinite number of species. Now, I suppose we all agree that this wouldn't do justice to the evolutionary species concept, don't we? However, I do think that the pattern in mitochondrial DNA described by Burbrink et al unveils a geneflow pattern which at least challenges our widely accepted concept of subspecies boundaries in Pantherophis obsoletus. From this point of view, colour really doesn't mean that much, as we all should know by now as members of a widely dispersed and highly diversified species.

Greetings,

Herman Bronsgeest.

Yes, Herman. Presented by you, the case would be very arguable. But to us lay people what happened was Burbrink said he saw some small differences in the genes, so he was just going to split this well accepted, long time species, into three species. It just didn't sit right at all.

Now, if you were going to say, we're going to argue how some differences in mtDNA are going to affect how we classify some common colubrids like P. obsoletus, it definitely is worth talking about. I would like to know how the genetics research works and just what it means evolutionarily, but with how it affects the standards we're used to. I think taxonomists still need to show some of the characteristics we've always used, such as scalation, general morphology, hemipene structure, microdermatics, distribution, behavior, something we can sink our teeth into.

I think Burbrink could have had a nice paper on how the Mississippi R. or Appalachian Mtns, or some other landform could have been a barrier to genetic dispersal at some time in history. But I don't think the evidence points to a needed split at this time, and I don't mean to imply that you do. Your stand is clear. We should discuss the differences in genes that he discovered and what might have caused that, but with today's dispersal and lack of other variation, imo the splitting won't fly, so he shouldn't be making that his immediate goal.

Sorry, if I sound redundant, but had to make that clear Would love to discuss this further, but I think we need facts from his paper to evaluate. Thanks and take care....

TC

Just a little reminder. If you are using genus Pantherophis for the American Rat Snakes and not Elaphe, then you need to change your species endings. Obsoleta becomes obsoletus and guttata becomes guttatus.