Taxonomy Study ROCKS Crotalus viridis World - VIDEO

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John Delgado
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Taxonomy Study ROCKS Crotalus viridis World - VIDEO

Post by John Delgado »

2013 Taxonomy Study Rocks Western Rattlesnake (Crotalus) World

A Master of Science Degree Thesis by Julianne R. Goldenberg rocks the Crotalus viridis taxonomy with new scientific evidence that may change species/subspecies in the Crotalus viridis and Crotalus oreganus world.

I am asking for help...,

Now, I have questions. Please FHF Nation... if there are people who understand this paper, and the video. I'm requesting open forum conversation related to understanding what all this means in laymen terms. "I'm a rattlesnake hunter Jim, NOT a scientist...!"

Please take the time to watch this video of Ms. Julianne R. Goldenberg.

To view the entire 81 page Thesis by Julianne R. Goldenberg SPECIAL NOTE: This video is approximately 90% scientific analysis and about 10% laymen -- Please try and stay with it and you will hear laymen explanation periodically through the video. And this is why I am asking for discussion of further explanation. I seriously hope we have some members here that understand this and will explain further... this is extremely fascinating.

Julianne Goldenberg- May 1, 2013
NACairns
Posts: 372
Joined: December 30th, 2013, 7:27 am

Re: Taxonomy Study ROCKS Crotalus viridis World - VIDEO

Post by NACairns »

Thanks for sharing. Here is how I saw this paper/video. I thought it was a very cool, labour intensive project especially for an MSc. There's a ton of theoretically heavy concepts most notably: what is a species. I would be cautious to say this rocks the world of of C. viridis taxonomy but would say it is a welcome addition to a contentious discussion of split or lump.

What she did that was the most novel about this is add neutral nuclear gene trees. To date mitochondrial DNA (mtDNA) has been only method used to tease these groups apart (see below). mtDNA is helpful and interesting especially for recent divergences as it has a smaller effective population size (inherited only through the mother so 50% of the pop) in which the frequency of a gene shifts more quickly than in nuclear DNA (nDNA; inherited from both parents). For each gene/loci you can make a tree similar to a species tree (but don't necessarily line up to a species trees; see incomplete linage sorting) which gives insight into the evolutionary history of that species/population/individual. mtDNA is inherited more or less as a single unit so each gene tells a similar story so adding nDNA allows her to tell a more complete story. I thought she did a good job but next time someone will do 20 loci or even resequence the whole genome so I would not say this is the final statement in this debate.

http://www.sciencedirect.com/science/ar ... 039990756X
http://clweb02.chrislands.com/clshops/S ... ouglas.pdf

Her methods were also novel to the this study system (C. viridis). The Bayesian method she used uses many repetitions of a model(s) to give a probability that said model is close to the "real" value. Neat stuff but very jargony and many people can likely speak to the intricacies of these methods better than I can (http://en.wikipedia.org/wiki/Bayes_factor).

I'll wait for these to make it through peer review process before I start changing the species on my photos but that does not mean that I necessarily I disagree with her findings but I think she may need to do some further sampling in some areas. That she separates C. o. oreganus with the southern species a sister species to C. o. helleri is interesting but her lack of sampling in the presumed contact zone between the two C. o. oreganus does not rule out that they freely interbreed and may in fact interbreed with C. o. helleri as well which would explain the divergence and similarities using isolation by distance. This might be an argument against elevating these clades.

She uses the evolutionary species concept which is interesting as it does not really address issues of reproductive isolation which is the focus of the more widely used biological species concept. Hybrids are well known in snakes including between well defined species of Crotalus (let alone subspecies) so elevating these may be difficult (see Diadophis).
http://www.jstor.org/stable/3892206?seq ... b_contents
http://www.bioone.org/doi/full/10.1894/ ... 2.0.CO%3B2

I thought it was a cool thesis and I await the peer-reviewed paper(s) it spawns.
All the best,
Nick
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