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The Good, the Bad, and the Ugly - Systematics
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by Cro on June 8, 2008
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Herpetotogical Systematics looks at the evolutionary history and relationships of Reptiles and Amphibians.
Herpetological Taxonomy is the science of classifying Reptiles and Amphibians into groups of related animals.
Often Systematics and Taxonomy go hand in hand. Or, Taxonomists often use Systematics to classify animals.
In the past, Reptiles and Amphibians were classified by the way they looked, where they were found, skeletal similarities, etc. These items are still in use, and still play a role. However.........
Classification is rapidly changing, due to the use of relatively new science that looks at the DNA of animals.
This can be good or bad, as there are unresolved issues in any science, and the results are subject to the interpetation of data by the researcher.
Now days, mDNA is often what is used to classify animals, however, it can create false relationships between animals, as it is not a complete analysis.
Before you comment in this thread, please read:
"Systematics and Herpetology in the Age of Genomics"
at:
http://www.redorbit.com/news/science/1419489/systematics_and_herpetology_in_the_age_of_genomics/
The article gives a good review of the use of mDNA, and the limits of mDNA, in the classification of Reptiles.
Will be interesting to hear what others think after they read the artile.
Best Regards John Z
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RE: The Good, the Bad, and the Ugly - Systematics
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by Crotalusssp on June 8, 2008
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John, Thank you very much for sharing this article. With advances in technology, (computer sequencing, PCR, etc), many of the problems that are encountered will hopefully begin to dissipate. I have never been a real fan of mDNA sequencing. The mitochondrial DNA is only inherited from the Mother and is rapidly evolving. With the technology now we are able to look at nuclear DNA, which is of course much larger, but should be more conclusive. I am very interested to see how the massive Colubrid family is broken down. Also, smaller scale species delineations should become clearer. Atriadactus may not only be recognized as a sub-species, but an all together new species entirely. Thanks again for sharing.
Charles
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RE: The Good, the Bad, and the Ugly - Systematics
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by Cro on June 10, 2008
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Charles, the research that is going on will change many things in Herpetology in the coming years.
Nuclear DNA studies will eventually replace mDNA in this research.
It is fasinating stuff, however, it is difficult for many folks to grasp these very technical ideas.
Best Regards John Z
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RE: The Good, the Bad, and the Ugly - Systematics
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by Crotalusssp on June 11, 2008
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John are you familiar with the theory of mitochondrial evolution in eukaryotic organisms? That is just side of mDNA you may find interesting. Dr. Lynn Margulis is responsible for much of the theory currently.
Charles
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RE: The Good, the Bad, and the Ugly - Systematics
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by Cro on June 11, 2008
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Charles, I have read some articles on that topic, however, need to learn a lot more.
I will check out the work of Dr. Lynn Margulis and see what he has to say.
Best Regards John Z
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RE: The Good, the Bad, and the Ugly - Systematics
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by Snakeman1982 on June 13, 2008
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Hey Guys,
I wouldn't go as far as saying that nuclear DNA will replace mtDNA but there have been quite a few more studies lately using nuclear DNA in reptilian lineages. Both however are replacing morphology in the study of vertebrate evolution. My thesis research looked at the phylogenetic relationships in a clade of Middle American pitvipers using morphology and there were a lot of good things about it and a lot of difficulties with it. Scientists aren't conducting morphological work as much anymore because it tends to be more time consuming, difficult to learn, and often doesn't give the most accurate results. Molecular biology has really revolutionized the way we investigate evolutionary relationships but there are certainly molecular studies and investigations that are inaccurate. However when done correctly, they tend to do a better and more accurate analysis of evolutionary relationships than morphology.
I tend to like morphology a lot because I think it allows you to see and understand the evolution of the animal from one species to the next. It is much more interesting to me than just examining a simple phylogenetic tree that is produced with molecular data. The problem that morphology has however is that there are usually very few characters (e.g., numbers of scales, shape of bones) whereas molecular data tend to use thousands of characters (i.e., A,C,G,T), which ultimately produces a stronger hypothesis for evolutionary relationships.
As far as pitvipers go, the best papers to read if you are interested in this subject are from Todd Castoe (his website has pdfs), Chris Parkinson (his website has pdfs), Ronald Gutberlet, Jr. (chapters in Biology of the Vipers and Venomous Reptiles of the Western Hemisphere), etc... John Wiens and Paul Chippendale have some excellent articles on morphological and molecular comparisons within the salamander clades. You can find all of Wiens' papers on his website at Stony Brook University. Just google his name.
Another great paper that discusses morphological vs. molecular phylogenetics is John Wiens' 2004 paper in Systematic Biology titled "The role of morphological data in phylogeny reconstruction."
Interesting topic,
Robert
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RE: The Good, the Bad, and the Ugly - Systematics
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by Snakeman1982 on June 13, 2008
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Just so I am not misunderstood, I guess I should mention that morphology isn't being replaced by DNA entirely. We still use it for tons of other studies in biology. Just less in phylogenetics. It is still very important in evolution, physiology, ecology, behavior, describing new species, natural history, etc... And it is critical in paleontology and investigating the relationships among extinct species.
Robert
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RE: The Good, the Bad, and the Ugly - Systematics
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by Crotalusssp on June 13, 2008
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Thanks for the list of papers. I will definitely go and check those out.
Charles
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