southern Utah

Share info and Pictures about gardens, parks, nurseries, and other locations with cacti.
A. Dean Stock
Posts: 458
Joined: Sat Oct 16, 2010 2:41 am
Location: 40 south 7440 east Kanab, Utah (Johnson Canyon)

Re: southern Utah

Post by A. Dean Stock »

DNA studies covers a lot of ground !! There are many ways to look at different DNA types. It is also getting to be much more reasonable money-wise to do a lot of this work. To the contrary, one can determine many species by DNA alone by using the proper repeat sequences/primers and the right computer technology. For instance, Lucas Majure is able to distinguish O. pottsii from O. macrorhiza and will probably have a lot to say about that problem in the future.
The real problem is twofold. First, there are very few graduate students that pursue DNA studies of cacti and second, without the field work to understand the morphological variation and hybriization, the DNA work can yield very wrong information. For instance, one current DNA study involving O. aurea and O. pinkavae unintenionally used hybrids for the DNA comparisons and retrieved O. polyacantha (actually O. erinacea) DNA contributed in the hybridization event. For this reason and others DNA studies of any kind must always be based on the best field work that uses morphology, ploidy, and distribution as seen in the work by Marc Baker referenced above by Peterb. I agree with Peterb that the use of species vs variety has been very unequally applied in cacti. One reason for this of course is in forms like Opuntia we often have little to go on except spine forms that vary a great deal. Chromosome counts helped a lot in understanding population differences but often were ignored as the good species boundaries that they presented. DNA data can help a lot in understanding how long a population has been isolated, geographically and/or genetically. and this data can then be used to better understand the appropriate taxnonomic level. The future will bring a much better understanding of plyletic and cladistic relationships of all cactus groups but we need many more people like Lucas Majure and Marc Baker.
Saxicola, I'd agree with you if we could always distinguish between good species and varieties but we often cannot. In the future, using appropriate morphological and DNA studies we may get closer to that goal. Contrary to your opinion, I think it is the most relevant of taxonomic pursuits.
Dean
Last edited by A. Dean Stock on Thu Dec 06, 2012 8:52 pm, edited 2 times in total.
Albert Dean Stock,Ph.D.
peterb
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Joined: Mon Aug 07, 2006 4:19 am
Location: Chandler, Arizona, USA

Re: southern Utah

Post by peterb »

Thanks again Dean! I would love to read about more recent innovations in DNA studies and how the level of detail has improved. I hope someone will either write such a piece or can point me toward one.

peterb
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Peterthecactusguy
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Joined: Fri Feb 19, 2010 7:49 am
Location: Black Canyon City, Arizona

Re: southern Utah

Post by Peterthecactusguy »

it is a fascinating subject. Thanks for the info Dean. :)
Here's to you, all you insidious creatures of green..er I mean cacti.
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