Reptile & Amphibian Forums

The following data is from Van Wallach (1998, Biology of the Reptilia, Vol. 19). The numbers given is the relative length of the intrapulmonary or right bronchus as a percentage of the right lung. 10 means the intrapulmonary bronchus is 10% as long as the right lung, and 90 means it is 90% as long as the right lung, for example.

Elaphe (Old World) 0.5-11
Coronella 4.2-6.6
Elaphe (New World) 11-21
Bogertophis 14-19
Pituophis 12-34
Arizona 46-91
Lampropeltis 27-58
Cemophora 73-75
Stilosoma 54
Rhinocheilus 85-86

Senticolis 2.3
Ptyas 0.2-1.7
Spalerosophis 1.3-3.5
Spilotes 0.7-1.6

From these figures and the generally accepted hypotheses of relationships among these snakes, it appears that the intrapulmonary bronchus started to increase within the Old World Elaphe, and that a species of Old World Elaphe with a relatively long intrapulmonary bronchus (at least 5-7% of the length of its right lung) migrated to the United States. This species is ancestral to Elaphe obsoleta, E. flavirufa and other species of New World Elaphe, as well as Bogertophis, Arizona, Lampropeltis, Stilosoma, Rhinocheilus and Cemophora. Senticolis triaspis is not a descendant of this species of Elaphe, since its intrapulmonary bronchus is much shorter (only 2.3%) and it is in fact closer to the racers than the New World ratsnakes. Based on morphology and the length of the intrapulmonary bronchus, the North American species of the Lampropeltini can be divided into two subgroups: the ratsnake group (Elaphe, Pituophis, Arizona, and Bogertophis) and the kingsnake group (Lampropeltis, Stilosoma, Rhinocheilus, Cemophora). Senticolis belongs to neither of these two groups. It may be part of Old World Elaphe or it may be a racer convergent upon the ratsnakes in morphology.

Bogertophis appears to be an early offshoot of the Lampropeltini, probably appearing as a genus before either Lampropeltis or Pituophis had evolved. Cemophora and Stilosoma appear to have descended from Lampropeltis. Arizona is most likely derived from Pituophis. The taxonomic position of Rhinocheilus is uncertain. It probably branched off just before the genus Lampropeltis evolved or alternatively it is a degenerate kingsnake.

Very interesting information on the intrapulmonary bronchus. That sheds a little more light on the situation.

You said:
>>From these figures and the generally accepted hypotheses of relationships among these snakes, it appears that the intrapulmonary bronchus started to increase within the Old World Elaphe, and that a species of Old World Elaphe with a relatively long intrapulmonary bronchus (at least 5-7% of the length of its right lung) migrated to the United States. This species is ancestral to Elaphe obsoleta, E. flavirufa and other species of New World Elaphe, as well as Bogertophis, Arizona, Lampropeltis, Stilosoma, Rhinocheilus and Cemophora. Senticolis triaspis is not a descendant of this species of Elaphe, since its intrapulmonary bronchus is much shorter (only 2.3%) and it is in fact closer to the racers than the New World ratsnakes. Based on morphology and the length of the intrapulmonary bronchus, the North American species of the Lampropeltini can be divided into two subgroups: the ratsnake group (Elaphe, Pituophis, Arizona, and Bogertophis) and the kingsnake group (Lampropeltis, Stilosoma, Rhinocheilus, Cemophora). Senticolis belongs to neither of these two groups. It may be part of Old World Elaphe or it may be a racer convergent upon the ratsnakes in morphology.
>>
My response:
I tend to think Senticolis is a basal member of the Elaphe, which could be fairly close to the racers...how close I don't know. Also, I would think that it's entirely possible for more than one species of Elaphe to have invaded North America, and that there could have been more than one invasion. So, there's several different possible scenarios for the evolution of the Lampropeltini.

You said:
>>Bogertophis appears to be an early offshoot of the Lampropeltini, probably appearing as a genus before either Lampropeltis or Pituophis had evolved. Cemophora and Stilosoma appear to have descended from Lampropeltis. Arizona is most likely derived from Pituophis. The taxonomic position of Rhinocheilus is uncertain. It probably branched off just before the genus Lampropeltis evolved or alternatively it is a degenerate kingsnake.
>>
My response:
I think Bogertophis probably evolved along with the development of the desert-like conditions in the area of the Mexican Plateau. It likely diverged to fill a niche from a more generalized ancestor, just as Pituophis and E. flavirufa did. Elaphe and Lampropeltis are both "Old Northern" genera according to Morafka ('77) and were undoubtedly around (during the Miocene) before any of the other Lampropeltini. Who knows exactly how many species of each could have lead to all the different species in the Lampropeltini today?

Thanks for the great info and lively discussion TC.

You wrote:
I tend to think Senticolis is a basal member of the Elaphe, which could be fairly close to the racers...how close I don't know. Also, I would think that it's entirely possible for more than one species of Elaphe to have invaded North America, and that there could have been more than one invasion. So, there's several different possible scenarios for the evolution of the Lampropeltini.

My response:
The most basal members of the ratsnakes clade (Old and New World) are Elaphe mandarina and E. conspicillata. It is tempting to believe that Senticolis is probably a bit more derived than E. mandarina since it is in the New World. Unfortunately that does not appear to be the case. The hemipenial structure of E. mandarina is actually closer morphologically to E. obsoleta than it is to Senticolis. E. mandarina is probably closer to E. obsoleta than either of them is to Senticolis, notwithstanding the trees of Utiger et al. and Rodiriguez-Robles, both of which show Senticolis as part of the Lampropeltini. You may believe that more than one species of Elaphe entered the New World but that seems unlikely since Old World Elaphe (including Coronella) lack the relatively long intrapulmonary bronchus that is found in New World Elaphe and the lampropeltine genera. If 2 Elaphe species entered the New World, then both had right bronchi that are at the top of the range for Old World Elaphe, which is certainly possible but probably unlikely. Further, if two species entered the US to give rise to the Lampropeltini, then the Lampropeltini should cluster into two separate groups, not one, unless both of the species of Elaphe are so closely related that they appear as one on the tree. The Lampropeltini forms a single monophyletic group, not two, even though the split between Elaphe obsoleta and Lampropelits came early, in the early Miocene, according to immunological data by Dowling et al.

Mr. Newton. Thanks for taking the time to research available resources and offering to discuss it with us on this forum. Unfortunately, non-university folks don't have the same resources to do this kind of work, but I'm happy to receive the info you presented. I did the best I could with what I've learned through the years to keep things moving. Now I'll have to study what you've presented, refigure my opinions/theories based on the new info, and get back to you later. Hopefully you'll hang around and be here in the future. TC.

I understand how you feel. We all have certain theories of what we think may have happened in the past. Even University folks have their theories. Sometimes those theories are confirmed but sometimes nature gives a surprising answer that contradicts them. Many morphologists thought that the bicolored kingsnakes evolved from the New World ratsnakes, and then later a bicolored kingsnake such as the common kingsnake is ancestral to the tricolored species. It all seems so logical but as things turn out, it is the tricolored species that are the oldest species in this genus (according to the fossil record) and the bicolored forms only evolved very recently in the Pleistocene. Very often, evolution does not take the shortest path. Many species, however, do take the shortest path available when moving between continents. There are no species of Elaphe on the west coast of the United States, but many are found on the eastern half. This is strong evidence that a European species of Elaphe had crossed a land bridge to N. America from Europe. Most of the New World Elaphe species are close relatives of E. obsoleta, for example E. vulpina and E. bairdi. Even E. guttata is a close relative of E. obsoleta. E. guttata hybridizes with E. obsoleta in nature and some individuals of E. guttata exhibit the 4-lined morph of E. obsoleta. Molecular data also show them to be close relatives. Pituophis is almost certainly the closest relative of E. obsoleta and most likely a direct descendant of it. The genus Lampropeltis, from which Rhinocheilus, Cemophora and Stilosoma may have evolved, is also a close relative of E. obsoleta according to hemipenial structure and DNA evidence. Lampropeltis may have evolved from an Elaphe obsoleta-like ancestor. E. flavirufa is not as closely related to Lampropeltis, Pituophis etc. But it, too, may be a close relative of E. obsoleta. Perhaps E. flavirufa is ancestral to both E. obsoleta and Lampropeltis. Senticolis, although popularly called a ratsnake, is almost certainly not closely related to either E. obsoleta or E. flavirufa or any of the 33 species of Old and New World Elaphe or to Lampropeltis. Even though there had been an initial rush to adopt Utiger et al.'s proposed taxonomy among many amateurs, many veteran herpetologists, especially those who are not cladists, will likely take a wait and see attitude. Others, like me, who are fully cognizant of Utiger et al.'s ideology and the reasons behind their proposal (namely an intolerance of paraphyletic taxa), will simply reject these proposals because they do NOT give us a better understanding of relationships among the ratsnakes. The ratsnakes do not form a polyphyletic group. It is a natural one. Keeping it in one genus tells us they are all closely related to each other and that they have not diverged morphologically from each other to any significant or measurable degree. Splitting them into a dozen or so genera mislead us into thinking that they are morphologically disparate when in fact they are not.

Paraphrasing Herndon Dowling (who made numerous contributions to the systematics of the genus Elaphe):

"At present we have some assurance that Elaphe obsoleta bears some relationship to Elaphe flavirufa and E. sauromates, but we would have no such assurance with Utiger et al.'s 'Pantherophis obsoletus' and 'Pseudelaphe flavirufa' which might be more closely related to Coluber constrictor, or to Drymarchon corais, or to some other species in so far as the nomenclature indicates."

Paraphrasing Herndon Dowling (who made numerous contributions to the systematics of the genus Elaphe):

"At present we have some assurance that Elaphe obsoleta bears some relationship to Elaphe flavirufa and E. sauromates, but we would have no such assurance with Utiger et al.'s 'Pantherophis obsoletus' and 'Pseudelaphe flavirufa' which might be more closely related to Coluber constrictor, or to Drymarchon corais, or to some other species in so far as the nomenclature indicates."

RS: Where does that quote come from? Is it a private correspondence?
John

It is not a direct quote. The original was published 10 years ago and it went like this:

"At present we have some assurance that Lampropeltis calligaster occipitolineata bears some relationship to L. calligaster, but we would have no such assurance with his "L. occipitolineata," which might be more closely related to L. getulus, or to L. triangulum, or to some other species in so far as the nomenclature indicates." (Dowling, H.G. 1993 A reply to Collins [l991,1992]. Herpetol. Rev. 24(1):11-13.)

What was applicable to L. c. occipitolineata applies equally to "Pantherophis" and "Pseudelaphe".

"There are no species of Elaphe on the west coast of the United States, but many are found on the eastern half. This is strong evidence that a European species of Elaphe had crossed a land bridge to N. America from Europe."

While I agree with the first half, I have to say 'not necessarily' with the second. There are several instances of plants that occur in Asia and on the East Coast of the US but do not occur on the West Coast or Europe. The Southern native Sweetgum tree (Thuja occidentalis) and Tulip Tree (Liquidambar styraciflua) would be monotypic were it not for a single relative each in China: Thuja orientalis & Liquidambar formosana. Also the stately Southern Magnolia (Magnolia grandiflora), Piedmont azalea (Rhododendron canescens), Lady Slipper Orchids (Cypripedium spp), Needle Palm (Rhapidophyllum histrix) & native bamboo (Arundinaria gigantea) have numerous relatives throughout Asia, but not a single representative on the West Coast. Also, I don't believe any near relatives of these plants are found naturally occurring in Europe, diminishing the notion of a land bridge populating the East coast. I believe that the climate and geology of the eastern US states proved to be a better fit for organisms from Asia and that space and time allowed them to thrive and diversify into the multitude of forms we see today.
-----
Who is like Set...

1.1 Vietnamese Blue Beauties
2.0 Taiwan Beauties
0.1 Bull Snake
1.0.0 Argentine Blk & Wht Tegu

A eastern North America to Europe land bridge is also supported by the distribution of the Old and New World water snakes. Natrix is a European genus that has a close relative (Nerodia) in the United States. At one time these two were classified as a single genus along with Regina, Clonophis, Seminatrix and Storeria. Natrix and Nerodia are nearly identical except for a small difference in number of chromosomes (2n=34 vs. 2n=36) and in hemipenial structure. Regina is intermediate between Natrix and Nerodia on the molecular tree and it has a hemipenis nearly identical to that of Natrix. A Natrix -> Regina -> Nerodia evolutionary sequence bridges the gap between Natrix and Nerodia. Natrix is not found in Asia and Nerodia in not found in the western United States. Therefore the most likely route is Europe to eastern N. America.

Great example, but has anyone considered the possibility that this group floated here on some type of rafting material? I mention this only because I don't see where a bridge from N America to Europe would have existed given what we believe regarding the expanse of the glacial ice sheet. The Bering Strait is obvious in its former existence and so is the bridge that connected Florida to Mexico. I imagine that Ireland could be perceived by some as the base of a bridge stretching to Greenland which would then provide access to N America due to the lowered sea levels during the Ice Age. Only problem with this is Ireland has no snakes because it was completely covered with ice at this time. I'd be more inclined to believe that water snakes populated islands that existed off the coast of Europe when the oceans were much lower and as the waters rose and submerged them, the snakes rode the flotsam to dry land. The snakes that ended up in Europe and the UK remained Natrix while those that reached N America eventually became Nerodia. Just my thoughts... not saying they're right.
-----
Who is like Set...

1.1 Vietnamese Blue Beauties
2.0 Taiwan Beauties
0.2 Cave Beauties
0.1 Bull Snake
1.0.0 Argentine Blk & Wht Tegu

"The Arctic islands of 50 million years ago were far different from the cold, treeless tundra of today. Fossil remains of crocodiles, turtles, lizards, monkey-like animals, large Metasequoia trees, lotuses and other plants describe a climate that was a frost-free, having a warm temperate climate similar to
present day South Carolina."

The quote above is from a web page describing a land bridge between North America and western Europe. The same land connection may have allowed newts (Triturus) to migrate from Europe to N. America. These newts then evolved into Notophthalmus.

The link to the web page is given below:
Ice mice first mammal to migrate from North America to Europe

You wrote:
Also the stately Southern Magnolia (Magnolia grandiflora), Piedmont azalea (Rhododendron canescens), Lady Slipper Orchids (Cypripedium spp), Needle Palm (Rhapidophyllum histrix) & native bamboo (Arundinaria gigantea) have numerous relatives throughout Asia, but not a single representative on the West Coast. Also, I don't believe any near relatives of these plants are found naturally occurring in Europe, diminishing the notion of a land bridge populating the East coast.

My response:
I am no botanist and plant evolution is off topic but since you use plants as an example to pooh-pooh my idea of a North America-Western Europe land bridge, here is a web page you may be interested in.

Some highlights from the web page:
"Using geophysically derived paleogeographies we propose the following. (1) Magnolias originated in westen North America and migrated eastward to Europe via the Thulean landbridge during the early Paleogene and from there into eastern Asia at some time not yet ascertained."
Contributions to the study of the Origin and Distribution of Magnolias from Paleomagnetism

"To analyse changes over time, we sorted biogeographic events into four major timeperiods using fossil, biogeographic and molecular evidence combined with a ‘branching clock’. These analyses show that trans-Atlantic distributions (EN–WP) were common in the Early–Mid Tertiary (70–20 Myr), whereas trans-Beringian distributions (WN–EP) were rare in that period. Most EN–EP disjunctions date back to the Early Tertiary(70–45 Myr), suggesting that they resulted from division of cross-Atlantic rather than cross-Beringian distributions."

The quote above comes from the authors of a paper analyzing animal dispersal in the holarctic from the late Mesozoic to the present. They find that dispersal from eastern North America to Europe was much more common than faunal exchanges between Asia and western North America during the early to mid-Tertiary period. It is during this period that an Old World species of Elaphe migrated to North America and became the ancestor of New World Elaphe and such lampropeltine genera as Lampropeltis, Pituophis, Arizona, Bogertophis, Cemophora, Stilosoma, and Rhinocheilus. Since two independent studies show that E. scalaris is the closest Old World relative of the New World lampropeltine genera, the western Europe to eastern North America route appears to be the most likely for this migration.
Patterns of animal dispersal in the holarctic

You wrote:
Many species, however, do take the shortest path available when moving between continents. There are no species of Elaphe on the west coast of the United States, but many are found on the eastern half. This is strong evidence that a European species of Elaphe had crossed a land bridge to N. America from Europe. Most of the New World Elaphe species are close relatives of E. obsoleta, for example E. vulpina and E. bairdi. Even E. guttata is a close relative of E. obsoleta. E. guttata hybridizes with E. obsoleta in nature and some individuals of E. guttata exhibit the 4-lined morph of E. obsoleta. Molecular data also show them to be close relatives. Pituophis is almost certainly the closest relative of E. obsoleta and most likely a direct descendant of it.

My response:
Pituophis is a ratsnake that occurs on the West Coast. According to Morafka, Pituophis and many species of New World Elaphe, Lampropeltis, Thamnophis, Storeria, Crotalus, and Sistrurus, evolved on the Mexican Plateau and in the Sierra Madres, along with the evolving ecosystems. At one time Europe, Asia, and North America were all connected as a huge landmass called Laurasia. According to Morafka, and probably others, Elaphe, Lampropeltis, Natrix, Coluber, Agkistodon, and probably some others were present in central N.A. during the Miocene, and probably late Oligocene, while the climate was changing from a warmer/wetter one to present conditions. A land bridge from Asia to N.A. was present at this time..Beringia. I don't know much about a N.A./European land bridge, but I'm sure it was present at some time during the existence of the super continent. The genera in question were holarctic, as were various plant species. There are numerous examples. Also, plant species may have spanned the continents well before the colubrid species evolved. Thus, colubrid snake species may have entered the New World, via a European connection, but likely entered via Beringia, as these species were holarctic when climate was favorable throughout all three continents at the time they evolved, and I don't know if there was a land connection with Europe during that time.

I saw your post after I posted information that could answer yours. According to a paper I found, the authors analyzed a large number of animal species phylogenetically and found the following:

"To analyse changes over time, we sorted biogeographic events into four major timeperiods using fossil, biogeographic and molecular evidence combined with a ‘branching clock’. These analyses show that trans-Atlantic distributions (EN–WP) were common in the Early–Mid Tertiary (70–20 Myr), whereas trans-Beringian distributions (WN–EP) were rare in that period. Most EN–EP disjunctions date back to the Early Tertiary(70–45 Myr), suggesting that they resulted from division of cross-Atlantic rather than cross-Beringian distributions."

What these authors found is that during the Paleocene, Eocene, Oligocene and Miocene, faunal exchanges between eastern North America and western Europe were much more common than faunal exchanges across the Bering Strait. This pattern is reversed from about 20 myr to the present. New World water snakes (Nerodia) are limited to the eastern US. Natrix, the genus of water snakes closest morphologically to Nerodia, is found only in Europe. Thamnophis, according to serum protein data, evolved from Nerodia. Thamnophis is found in the western United States. The evolution of the natricine snakes suggest that they originated in the east and migrated from east to west.

Your hypothesis is that colubrid snakes entered the US from the Old World during the late Oligocene to Miocene. During this time period a Thulean land bridge connects eastern North America with Europe, and the climate was temperate, allowing many temperate to subtropical species to cross this land bridge. Apparently Elaphe is one of those that made the crossing. The species of Old World Elaphe closest to the New World species of Elaphe and lampropeltine snakes is, according to both Utiger et al. and Lopez and Maxson: Elaphe scalaris. Either some individuals of this particular species made the journey to North America or a very closely related species did. Yes, Pituophis does occur on the west coast, but it is a derived genus. It is most likely a direct descendant of Elaphe obsoleta but not vice versa. Other derived species that have made it to the west coast include Lampropeltis, Arizona, Rhinocheilus, and, to a lesser extent, Bogertophis. These species are not ancestral to New World Elaphe, but they are almost certainly descended from a species of New World Elaphe. The dispersal pattern of the New World Elaphe and lampropeltine species appear similar to the natricine snakes: all of the basal species are confined to the east, whereas the derived species are found over the entire continent. The possibility that a racer-like ratsnake is ancestral to Senticolis, Elaphe, and Lampropeltis et al. is very slim considering the biogeographic evidence in addition to the morphological and molecular evidence. Utiger et al. and Rodriguez-Robles are both mistaken if they think that Senticolis is part of the Lampropeltini.
Holarctic Animal Dispersal Patterns

You wrote:
What these authors found is that during the Paleocene, Eocene, Oligocene and Miocene, faunal exchanges between eastern North America and western Europe were much more common than faunal exchanges across the Bering Strait. This pattern is reversed from about 20 myr to the present.

My response:
Maybe there were large exchanges of fauna via a N. A. - w. European land bridge before the end of the Miocene. I haven't had a chance to research this idea, yet. Certainly there was at least some chance of a Beringia migration, however, as this bridge was open too. Also, the Young Northern (modern) species (Morafka) didn't evolve until less than 15 mya. The ancestors of Elaphe, Lampropeltis, Nerodia, and Coluber could have been here before 20 mya, and could have come via Asia or, possibly, w. Europe.

You wrote:
New World water snakes (Nerodia) are limited to the eastern US. Natrix, the genus of water snakes closest morphologically to Nerodia, is found only in Europe. Thamnophis, according to serum protein data, evolved from Nerodia. Thamnophis is found in the western United States. The evolution of the natricine snakes suggest that they originated in the east and migrated from east to west.

My response:
Nerodia is limited to the Eastern U. S. now, but 20 mya it was a different story. The Old Northern (Morafka) stock was holarctic in distribution. Favorable habitat could be found in the Western U. S., as well as the East. According to Morafka, Thamnophis was derived on the Mexican Plateau from a Nerodia ancestor, and the same was true for many other genera, i.e. Lampropeltis, Elaphe, etc.

You wrote:
Your hypothesis is that colubrid snakes entered the US from the Old World during the late Oligocene to Miocene. During this time period a Thulean land bridge connects eastern North America with Europe, and the climate was temperate, allowing many temperate to subtropical species to cross this land bridge. Apparently Elaphe is one of those that made the crossing. The species of Old World Elaphe closest to the New World species of Elaphe and lampropeltine snakes is, according to both Utiger et al. and Lopez and Maxson: Elaphe scalaris. Either some individuals of this particular species made the journey to North America or a very closely related species did.

My response:
The climate at this time was temperate to subtropical and much more humid than today across N. A. It's possible that colubrid ancestors crossed the Bering Straits Land Bridge in the early Miocene. It's also possible that they crossed both land bridges. I'm not sure (Elaphe) scalaris, now split into Rhinechis (sp?), is old enough to be a Lampropeltini ancestor. This species probably evolved in the Pliocene or later. And how could a species so different from E. schrencki, dione, quatuorlineata, etc, that it was split into a separate genus, be the ancestor of the Lampropeltini and the other mentioned species? I think the Elaphe/Lampropeltini ancestor was a much older species, or more than one, that had subtropical adaptations.

You wrote:
Yes, Pituophis does occur on the west coast, but it is a derived genus. It is most likely a direct descendant of Elaphe obsoleta but not vice versa. Other derived species that have made it to the west coast include Lampropeltis, Arizona, Rhinocheilus, and, to a lesser extent, Bogertophis. These species are not ancestral to New World Elaphe, but they are almost certainly descended from a species of New World Elaphe. The dispersal pattern of the New World Elaphe and lampropeltine species appear similar to the natricine snakes: all of the basal species are confined to the east, whereas the derived species are found over the entire continent. The possibility that a racer-like ratsnake is ancestral to Senticolis, Elaphe, and Lampropeltis et al. is very slim considering the biogeographic evidence in addition to the morphological and molecular evidence. Utiger et al. and Rodriguez-Robles are both mistaken if they think that Senticolis is part of the Lampropeltini.

My response:
The ancestral Elaphe, Lampropeltis, and Natrix species migrated south in N. A. as the climate cooled, and gave rise to many other Lampropeltine species on the Mexican Plateau and in the Sierra Madres. These offshoots included Pituophis, Thamnophis, the main radiation of Lampropeltis, and several Elaphe species. Most of the basal species are confined to the Mexican highlands, except species that can no longer thrive there, like the Nerodia. Bogertophis, Elaphe flavirufa, and Pituophis all evolved there, probably from the ancient Elaphe ancestor. Whether Senticolis is involved with the Elaphe ancestor, or a racer ancestor remains to be seen from further studies. I don't think Elaphe obsoleta can be the direct ancestor of the Lampropeltini, or even the New World Elaphe, because it isn't centered in the subtropics, nor do I think it's an old enough species to be the ancestor.

I would give more evidence for my main theory and other ideas, but I've been working and traveling a lot and just don't have enough free time right now. I want to do some more research too.

BTW, I read a paper today called, "Mammals and Land Bridges", by George Gaylord Simpson (1940), which showed a map (fig. 2) of the full range of Mastodonts covering northern Africa, Eurasia, and N. America. The only connection bt. Eurasia and N. A. was the Bering Straits Land Bridge, and the time frame was the Miocene. I know it's an old paper, but tells me that this land bridge was open to migration for other animals, like snakes, also.

Terry wrote:
Maybe there were large exchanges of fauna via a N. A. - w. European land bridge before the end of the Miocene. I haven't had a chance to research this idea, yet. Certainly there was at least some chance of a Beringia migration, however, as this bridge was open too. Also, the Young Northern (modern) species (Morafka) didn't evolve until less than 15 mya. The ancestors of Elaphe, Lampropeltis, Nerodia, and Coluber could have been here before 20 mya, and could have come via Asia or, possibly, w. Europe.

My response:
Molecular data show that many genera of New World snakes, including Elaphe, probably migrated from the Old World in the late Oligocene to early Miocene, when most (but not all) faunal exchanges occurred via the Thulean land bridge between eastern North America and western Europe. Later faunal exchanges are more common via the Beringia land bridge. As I said, the distribution of Elaphe and Nerodia support a Thulean land bridge crossing, not a Beringia land bridge crossing.

Terry wrote:
Nerodia is limited to the Eastern U. S. now, but 20 mya it was a different story. The Old Northern (Morafka) stock was holarctic in distribution. Favorable habitat could be found in the Western U. S., as well as the East. According to Morafka, Thamnophis was derived on the Mexican Plateau from a Nerodia ancestor, and the same was true for many other genera, i.e. Lampropeltis, Elaphe, etc.

My response:
The ribbon snakes, which are intermediate between the garter and water snakes, do not appear to have originated on the Mexican Plateau. Garter snakes are also found on the east coast, even though they are the only natricines that have made it to the west coast. The distribution of these taxa does not support Morafka’s speculation.

Terry wrote:
The climate at this time was temperate to subtropical and much more humid than today across N. A. It's possible that colubrid ancestors crossed the Bering Straits Land Bridge in the early Miocene.

My response:
That is very unlikely since most faunal exchanges during the time period were using the Thulean land bridge between eastern North America and western Europe.

Terry wrote:
It's also possible that they crossed both land bridges. I'm not sure (Elaphe) scalaris, now split into Rhinechis (sp?), is old enough to be a Lampropeltini ancestor. This species probably evolved in the Pliocene or later.

My response:
What evidence, if any, do you have that E. scalaris evolved in the Pliocene or later? DNA data shows that it is basal to New World Elaphe and the Lampropeltini.

Terry wrote:
And how could a species so different from E. schrencki, dione, quatuorlineata, etc, that it was split into a separate genus, be the ancestor of the Lampropeltini and the other mentioned species? I think the Elaphe/Lampropeltini ancestor was a much older species, or more than one, that had subtropical adaptations.

My response:
Very good question! That is one point I was trying to make all along. Elaphe scalaris is not different enough from other species of Old World Elaphe to deserve being placed in a different genus. Utiger et al., who splinter Elaphe into a dozen or so genera, do not even try to tell us why they do it. They certainly give us no definition for most of the genera they recognize. One will search in vain for descriptions of differences among these dozen or so undefined and probably undefinable genera. What is the difference between, say, “Pantherophis obsoletus” and “Pseudelaphe flavirufa”? Utiger et al. do not say. You may ASSUME that there is a difference because Elaphe obsoleta and Elaphe flavirufa are placed in difference genera, but that assumption is incorrect. So, just because Elaphe scalaris has been dumped into a genus of its own does not mean that it is so different from “Pantherophis obsoletus” that it cannot be ancestral to it. Besides, the king crab is so different from a hermit crab that it could not have evolved from a species of hermit crab, right? Wrong! The king crab is descended from a species of hermit crab according to molecular data, which confirms earlier suspicions of insightful scientists who suspected that such a relationship may exist because of morphological similarities between these disparate taxa. Molecular data shows that E. scalaris is probably ancestral to New World Elaphe.

Elaphe scalaris lives in western Europe, making it a prime candidate as the ancestor of New World Elaphe, since it is in a position to cross the Thulean land bridge between western Europe and eastern N. America in the late Oligocene and Miocene. E. scalaris is a warm temperate/subtropical species living in southern France, Portugal and Spain. Its range probably extended farther north in the Oligocene and Miocene when the arctic areas were warm temperate in climate.

Terry wrote:
The ancestral Elaphe, Lampropeltis, and Natrix species migrated south in N. A. as the climate cooled, and gave rise to many other Lampropeltine species on the Mexican Plateau and in the Sierra Madres. These offshoots included Pituophis, Thamnophis, the main radiation of Lampropeltis, and several Elaphe species. Most of the basal species are confined to the Mexican highlands, except species that can no longer thrive there, like the Nerodia. Bogertophis, Elaphe flavirufa, and Pituophis all evolved there, probably from the ancient Elaphe ancestor. Whether Senticolis is involved with the Elaphe ancestor, or a racer ancestor remains to be seen from further studies. I don't think Elaphe obsoleta can be the direct ancestor of the Lampropeltini, or even the New World Elaphe, because it isn't centered in the subtropics, nor do I think it's an old enough species to be the ancestor.

My response:
I know Morafka’s speculation is dear to your heart. His speculation is interesting, but it has been refuted by molecular data which began to emerge a few years after he wrote his book. If he is writing the book now, he would most likely come to a different conclusion because of the available evidence. Pituophis almost certainly evolved in the east. The distribution of Pituophis melanoleucus melanoleucus suggests that it has been driven south by the last glaciation, since isolated pockets of remants are still found to the North. The distribution of gopher snakes in the northwest suggests that they had only recently moved north after the last glacial period. The Mexican species of Pituophis are more closely related to the gopher snakes of the western United States than either of them is to the pine snakes both morphologically and in genetic distance. Senticolis is almost certainly not a part of the New World Elaphe-Lampropeltini clade. Its lung is the same as those of the racers. All of the New World ratsnakes and lampropeltines have the intrapulmonary bronchus, as do Elaphe scalaris, if I read Van Wallach correctly. Senticolis does not. Elaphe obsoleta is an indisputably old species because there is a lot of intraspecific genetic variation. Since such variation can only accumulate slowly over time, Elaphe obsoleta has been around a long time. It is an old species.

Terry wrote:
I would give more evidence for my main theory and other ideas, but I've been working and traveling a lot and just don't have enough free time right now. I want to do some more research too.

BTW, I read a paper today called, "Mammals and Land Bridges", by George Gaylord Simpson (1940), which showed a map (fig. 2) of the full range of Mastodonts covering northern Africa, Eurasia, and N. America. The only connection bt. Eurasia and N. A. was the Bering Straits Land Bridge, and the time frame was the Miocene. I know it's an old paper, but tells me that this land bridge was open to migration for other animals, like snakes, also.

My response:
Simpson is a great mammalogist, paleontologist, evolutionary biologist and above all, a great scientist. Like all great scientists, he is not afraid to admit he is wrong or to change his mind if his theory is contradicted by evidence. Like all scientists, he must base his theory on known facts. In the 1940’s the only known migratory route for mammals was the Beringia land bridge. It isn’t until 2001 that the first documented evidence of a North America-western Europe mammalian migration across the Thulean land bridge is recorded (see the link to the web page of this discovery below). If Simpson is still with us, and if he is writing a book or a paper, he will take the new evidence into account. Yes, the Beringia land bridge is open to faunal exchanges, and it is the predominant route in the Pliocene and Pleistocene. During the early to mid Tertiary, however, the eastern North America-western Europe faunal exchanges far outnumber those that utilized the Beringia land bridge. It is during the early to mid-Tertiary that the ancestor of New World Elaphe and the lampropeltine snakes migrated to the New World. Based on present day distribution of New World Elaphe and the available molecular data, the odds are overwhelmingly in favor of Elaphe scalaris being the direct ancestor of New World Elaphe and the Lampropeltini, and the most likely migratory route is western Europe to eastern North America, across the Thulean land bridge.
Ice mice first mammal to migrate from North America to Europe

You said:
>>Molecular data show that many genera of New World snakes, including Elaphe, probably migrated from the Old World in the late Oligocene to early Miocene, when most (but not all) faunal exchanges occurred via the Thulean land bridge between eastern North America and western Europe. Later faunal exchanges are more common via the Beringia land bridge. As I said, the distribution of Elaphe and Nerodia support a Thulean land bridge crossing, not a Beringia land bridge crossing.

My response:
I don't agree with this theory. I read a paper today from "The Flora of North America", Chapter 3...History of N. A. Vegetation, by Alan Graham. Page six...he talks about the two land bridges and states that...Land connection between North America and Asia existed for much of the early Tertiary via the Bering land bridge (D.M.Hopkins 1967), and perhaps until later in the Tertiary (J.T.Parrish 1987, p.61). To the northeast, North America was connected to Europe by the sundered landmass of Euramerica (fig. 3.4), which existed at the end of the Paleocene but was beginning to fragment by the early Eocene.

I'm sure the deciduous forest vegetation was holarctic throughout much of the Miocene, spanning both land bridges, but the Thulean land bridge was ineffective after the Eocene, let alone in the Miocene. The Elaphe ancestor was most likely an invader from Asia across Beringia.

You wrote:
>>What evidence, if any, do you have that E. scalaris evolved in the Pliocene or later? DNA data shows that it is basal to New World Elaphe and the Lampropeltini.

My response:
Most of the "Young Northern" species evolved in the late Miocene or Pliocene. I assumed it was a Young Northern species since it was close to the Lampropeltini and the Elaphe (quatuorlineata, schrencki, etc.) Maybe it's a little older, but not old enough to be the Elaphe ancestor I don't think. The Eurasian species, taeniura/moellendorffi group, are more basal and older, and closer to the ancestral Elaphe, imo. Also, I believe many of the Elaphe are direct descendants from this core group. Scalaris is adapted to a dry, temperate climate, and is unlikely to have made a land bridge crossing through extensive, humid, deciduous woodlands, even if it crossed at the Bering Straits land bridge. I think a Far Eastern Elaphe ancestor is more logical.

You wrote:
>>I know Morafka’s speculation is dear to your heart. His speculation is interesting, but it has been refuted by molecular data which began to emerge a few years after he wrote his book. If he is writing the book now, he would most likely come to a different conclusion because of the available evidence. Pituophis almost certainly evolved in the east.

My response:
Your evidence for the statements about Pituophis is not compelling. I still think they evolved in the Mexican Highlands. The s. Mexican species is closest to the ancestral Elaphe. And what is it about Morafka's work that has been refuted by molecular data? I still like Morafka, even if he is outdated. He had some good ideas and I would have to see the evidence to agree that his conclusions are all wrong.
Flora of North America...link

Terry wrote:
I don't agree with this theory. I read a paper today from "The Flora of North America", Chapter 3...History of N. A. Vegetation, by Alan Graham. Page six...he talks about the two land bridges and states that...Land connection between North America and Asia existed for much of the early Tertiary via the Bering land bridge (D.M.Hopkins 1967), and perhaps until later in the Tertiary (J.T.Parrish 1987, p.61). To the northeast, North America was connected to Europe by the sundered landmass of Euramerica (fig. 3.4), which existed at the end of the Paleocene but was beginning to fragment by the early Eocene.

My response:
I found your passage. The author went on to say the following “Two routes for migration existed. There was a southern one along the Greenland-Scotland Ridge (the Thulean route, ca. 45°--50° N paleolatitude), disrupted in the early Eocene, but possibly providing land surfaces from North America east to Iceland until the Miocene.”

If some European species had made it to Iceland earlier, before the disruption, than a connection to North America across the Thulean route remains passable until the Miocene. Therefore, there is nothing that will stop a European species of Elaphe from entering North America until at least the end of the Oligocene.

Terry wrote:
“I'm sure the deciduous forest vegetation was holarctic throughout much of the Miocene, spanning both land bridges, but the Thulean land bridge was ineffective after the Eocene, let alone in the Miocene. The Elaphe ancestor was most likely an invader from Asia across Beringia.

My response:
Not so. The passage you did not quote from the article clearly shows that animals that had made their way to Iceland have free access to North America until the Miocene. Iceland during the Eocene and earlier periods was warm. “Surface marine water temperature bordering east Greenland was about 17°C in the late Cretaceous, and about 15° C bordering Ellesmere Island during the middle Eocene.”

I wrote:
>>What evidence, if any, do you have that E. scalaris evolved in the Pliocene or later? DNA data shows that it is basal to New World Elaphe and the Lampropeltini.

Terry wrote:
Most of the "Young Northern" species evolved in the late Miocene or Pliocene. I assumed it was a Young Northern species since it was close to the Lampropeltini and the Elaphe (quatuorlineata, schrencki, etc.) Maybe it's a little older, but not old enough to be the Elaphe ancestor I don't think. The Eurasian species, taeniura/moellendorffi group, are more basal and older, and closer to the ancestral Elaphe, imo. Also, I believe many of the Elaphe are direct descendants from this core group. Scalaris is adapted to a dry, temperate climate, and is unlikely to have made a land bridge crossing through extensive, humid, deciduous woodlands, even if it crossed at the Bering Straits land bridge. I think a Far Eastern Elaphe ancestor is more logical.

My response:
E. scalaris may not have made the crossing into North America, but its descendant(s) may have. Elaphe obsoleta and the pine snakes (Pituophis melanoleucus) are not tropical species; neither are the basal members of Lampropeltis (the tricolors). E. obsoleta/vulpina would be suitable descendant species of E. scalaris. It is probably the descendant species of E. scalaris that finally entered the U. S. Senticolis may have entered North America across the Bering Strait, but the ancestor of E. obsoleta most likely entered via the Thulean land bridge, given the present distribution not only of E. obsoleta but the genus as a whole in North America.

Terry wrote:
Your evidence for the statements about Pituophis is not compelling. I still think they evolved in the Mexican Highlands. The s. Mexican species is closest to the ancestral Elaphe. And what is it about Morafka's work that has been refuted by molecular data? I still like Morafka, even if he is outdated. He had some good ideas and I would have to see the evidence to agree that his conclusions are all wrong.

My response:
I speculated that Pituophis evolving in the east on the basis of zoogeography and morphology. Since then I have gone to the library and checked the following paper:

Rodriguez-Robles, Javier A. and Jose M. De Jesus-Escobar. 2000. Molecular Systematics of New World Gopher, Bull, and Pinesnakes Pituophis:Colubridae), a Transcontinenatal Species Complex. Molecular Phylogenetics and Evolution, Vol 14, No 1, pp 35-50

According to the mtDNA data, the pine snakes (eastern subspecies of P. Melanoleucus) evolved first and the species then spread towards the west. If Morafka believes that Pituophis evolved on the Mexican Plateau, his theory has been contradicted by molecular data.

RS said:
>>I speculated that Pituophis evolving in the east on the basis of zoogeography and morphology. Since then I have gone to the library and checked the following paper:
>>
>>Rodriguez-Robles, Javier A. and Jose M. De Jesus-Escobar. 2000. Molecular Systematics of New World Gopher, Bull, and Pinesnakes Pituophis:Colubridae), a Transcontinenatal Species Complex. Molecular Phylogenetics and Evolution, Vol 14, No 1, pp 35-50
>>
>>According to the mtDNA data, the pine snakes (eastern subspecies of P. Melanoleucus) evolved first and the species then spread towards the west. If Morafka believes that Pituophis evolved on the Mexican Plateau, his theory has been contradicted by molecular data.

My response:
Thanks very much for the lead on this literature. Is this paper on-line by any chance? It sounds like an interesting read. I wish I had more time to pursue the literature. I'd like to find some molecular studies on racers too. Anyway, I'll look into this new info and see if I have to revise my stance on Pituophis.

All in all, it's been an interesting discussion on the possibilities of the Elaphe evolution. I would say that two routes for the ancestral Elaphe were possible, even though we don't agree on the likely ancestor. I also think Utiger et al. went too far in the splitting of genera from the Elaphe. For now, I will keep using Elaphe for scalaris, the taeniura/moellendorffi group, and the new Elaphe group (quatuorlineata, schrencki, etc.). I can see where you want to keep Elaphe, instead of Pantherophis for the New World Elaphe, but I kind of like Pantherophis, and will explain why when I have more time. I definately like Oreophis and Zamenis, and will explain more later, and will probably have to go with Euprepiophis, even though they're most likely ratsnakes, and I'll explain more later.

The molecular, or mtDNA testing is pretty interesting the way it's affecting how we think about taxonomy and evolution. Although I've resisted accepting this evidence in the past, I can see now that I'll have to start using it the best I can to be able to understand future changes in taxonomy. Keep pluggin and helping us to find this kind of material. TC.

Unfortunately the Pituophis paper is not online for free. If you have access to a University library catalog electronically and a password then you can access it online for free.

As for the names, I put convenience way down the list of priorities. Polyphyly is number 1 and morphological disparity is number 2 among the reasons I either reject or accept new names. "Pantherophis" is a convenient short hand for New World Elaphe, although it is not a good one even for that purpose, since E. flavirufa has been put in Pseudelaphe by Utiger et al. As for the other names, I will simply ignore them since they do not inform us about relationships. One thing to remember about DNA evidence is that they do not inform us of morphological disparity. They can only tell us branching order and they are very good at that. A balanced classification requires more than just branching order; it requires an evaluation of morphological disparity. Since Utiger et al. do not evaluate morphological disparity at all, their classification is purely based on branching order. Further, their ideological intolerance of paraphyletic taxa make their classification too destructive and unstable to be useful. Classifications are artificial constructs. Taxonomists spend time classifying animals because stable classifications can facilitate communication, permit formulation of scientific thought and information retrieval. An unstable and destructive taxonomy, such as Utiger et al.'s splintering of Elaphe, violate all of the reasons why taxonomists classify in the first place. Hence it is really in the best interest of science not to accept the cladists' intolerance of paraphyletic taxa in general and Utiger et al.'s intolerance of paraphyletic Elaphe in particular.