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CLIMATE CHANGE AND EVOLUTION OF THE NEW WORLD PITS
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by ChuckHurd on May 26, 2009
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CNAH ANNOUNCEMENT
The Center for North American Herpetology
Lawrence, Kansas
http://www.cnah.org
26 May 2009
CLIMATE CHANGE AND EVOLUTION OF THE NEW WORLD PITVIPER GENUS AGKISTRODON
(VIPERIDAE)
Michael E. Douglas, Marlis R. Douglas, Gordon W. Schuett and Louis W. Porras
2009. Journal of Biogeography 36: 1164-1180
Abstract:
Aim: We derived phylogenies, phylogeographies, and population demographies for two
North American pitvipers, Agkistrodon contortrix (Linnaeus, 1766) and A. piscivorus
(Lacepede, 1789) (Viperidae: Crotalinae), as a mechanism to evaluate the impact of rapid
climatic change on these taxa.
Location: Midwestern and eastern North America.
Methods: We reconstructed maximum parsimony (MP) and maximum likelihood (ML)
relationships based on 846 base pairs of mitochondrial DNA (mtDNA) ATPase 8 and
ATPase 6 genes sequenced over 178 individuals. We quantified range expansions,
demographic histories, divergence dates and potential size differences among clades
since their last period of rapid expansion. We used the Shimodaira–Hasegawa (SH) test to
compare our ML tree against three biogeographical hypotheses.
Results: A significant SH test supported diversification of A. contortrix from northeastern
Mexico into midwestern–eastern North America, where its trajectory was sundered by two
vicariant events. The first (c. 5.1 Ma) segregated clades at 3.1% sequence divergence (SD)
along a continental east–west moisture gradient. The second (c. 1.4 Ma) segregated clades
at 2.4% SD along the Mississippi River, coincident with the formation of the modern Ohio
River as a major meltwater tributary. A single glacial refugium was detected within the
Apalachicola region of southeastern North America. Significant support was also found for
a hypothesis of trans-Gulf rafting by the common ancestor of A. piscivorus from eastern
Mexico (possibly the Yucatan Peninsula) to northern Florida. There, a Mid–Late Pliocene
marine transgression separated it at 4.8% SD from mainland North America. Significant
range expansions followed compressive glacial effects in three (of four) A. contortrix
clades and in two (of three) A. piscivorus clades, with the Florida A. piscivorus clade
exhibiting significant distributional stasis.
Main conclusions: Pliocene glaciations, rapidly developing western aridity, and Pleistocene
glacial meltwaters seemingly led to the diversification of A. contortrix and A. piscivorus in
North America. Both species were pushed southwards by Pleistocene climate change, with
subsequent northward expansions uninhibited topographically. The subspecific taxonomy
used for A. contortrix and A. piscivorus today, however, appears non-representative. The
monophyletic Florida subspecies of A. piscivorus may be a distinct species (at 4.8% SD),
whereas two western subspecies of A. contortrix also appear to constitute a single distinct
species, pending additional analyses. We conclude that both species of Agkistrodon can be
used as suitable ectothermic models to gauge impacts of future climate change.
*****
CNAH Note: Based on the data analyzed, in this paper the following subspecies do not
appear to be supported by evidence: Agkistrodon piscivorus leucostoma, Agkistrodon
contortrix mokasen, Agkistrodon contortrix phaeogaster, and Agkistrodon contortrix
pictigaster.
Apparently, the Cottonmouth consists of two species, Agkistrodon piscivorus (Northern
Cottonmouth) and Agkistrodon conanti (Southern Cottonmouth), and the Copperhead
consists of two species, Agkistrodon contortrix (Eastern Copperhead) and Agkistrodon
laticinctus (Western Copperhead).
*****
A gratis PDF of this article is available from the CNAH PDF Library at
http://www.cnah.org/cnah_pdf.asp
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RE: CLIMATE CHANGE AND EVOLUTION OF THE NEW WORLD
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by ChuckHurd on May 26, 2009
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One positive that I see, if this research holds up and is accepted, the broad band and trans pecos copperheads will not be legal to keep in GA and AL.
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RE: CLIMATE CHANGE AND EVOLUTION OF THE NEW WORLD
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by Cro on May 26, 2009
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Interesting article, as it to a large extent agrees with the conclusions reached in the previous study by T.J. Guiher, F.T. Burbrink.
The only real difference is these authors want us to wind up with two copperheads and two cottonmouths, and the deviding lines for the populations have changed a bit.
The previous authors wanted us to wind up with three copperheads and two cottonmouths.
I know that T.J. Guiher, F.T. Burbrink are continuing the work they started and continue to collect DNA samples of animals in the study. We should see a update on that material probably next year.
As far as the broad-banded copperhead, trans-pecos copperhead, osage copperhead, and northern copperhead, they will not exist anymore. They will have vanished from scientific nominclature,just as the canebrake rattlesnake has, however, that will not stop herpers from calling them by the old names.
This should be fun to watch. Perhaps in a two or three more years, they will have it all sorted out.
Best Regards
John Z
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RE: CLIMATE CHANGE AND EVOLUTION OF THE NEW WORLD
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by AquaHerp on May 26, 2009
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Ugh. Well have to type them according to venoms like the mojaves.
DH
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RE: CLIMATE CHANGE AND EVOLUTION OF THE NEW WORLD
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by ChuckHurd on May 26, 2009
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Watch for the return of the canebrake! Gordon uses DNA from my locality specific snakes. It is his opinion, which he will show through evidence when he releases the research paper, that the cane and timber are a separate species. At some point he will be suggesting Crotalus atricaudatus.
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RE: CLIMATE CHANGE AND EVOLUTION OF THE NEW WORLD
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by pictigaster1 on May 26, 2009
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Will this ever just go away no. Every one wants to change the world one snake at a time.The current is just fine.
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RE: CLIMATE CHANGE AND EVOLUTION OF THE NEW WORLD
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by Cro on May 26, 2009
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"At some point he will be suggesting Crotalus atricaudatus."
Would not surprise me if we see that someday. Hopefully soon, so we can get it out of the way. Will be very interesting to see the data, as that could be a very big can of worms.
Of course, this copperhead / cottonmouth thing just might turn into one also.
This whole thing is starting to remind me of the proposed new classifications that Hoser came up with a few months ago.
Perhaps sometimes it is best to leave things the way the were. If it is not broke, do we really need to be fixing it ?
Best Regards
John Z
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RE: CLIMATE CHANGE AND EVOLUTION OF THE NEW WORLD
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by agkistrodude on May 26, 2009
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Crotalus h. atricaudatus has never left my hot room. I would love to see C. atricaudatus.
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RE: CLIMATE CHANGE AND EVOLUTION OF THE NEW WORLD
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by Adamanteus70 on May 28, 2009
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"Crotalus h. atricaudatus has never left my hot room" - Me neither!
I will always refer to them as Canebrakes.
And Hoser can forget it if he thinks I am going to call adamanteus by any other name!
John's right, if it is not broke, do not even try to fix it!
Thanks for posting this Chuck. Am I going to see you next month?
Paul
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RE: CLIMATE CHANGE AND EVOLUTION OF THE NEW WORLD
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by ChuckHurd on May 28, 2009
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No sir, barring something completely unexpected, I will never attend another show that Repticon or Cathy has anything to do with. They allowed my friend Tom to drive all the way to SC last show before they decided to tell me that we had been replaced to do the venomous exhibit. Cathy refused to even speak to me when I called and Gary would not return my calls. I know the show is over the top right now…lots of venders, lots of people…no one is going to miss my $8, however, actions like this are exactly what lead to the end for Tony.
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