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AlbertKLloyd

Cladistic Analysis Of Trichocereus (issues)

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http://www.cactusconservation.org/CCI/library/pdf/Albesiano_Terrazas_2012_Haseltonia_17_3-23.pdf

Cladistic Analysis Of Trichocereus (Cactaceae: Cactoideae:

Trichocereeae) Based On Morphological DATA And Chloroplast

Dna Sequences

Sof ía Albesiano

I wanted to address and discuss this paper.

It is based on chloroplast sequences and morphological data.

Here is one of its vital flaws, if you cross two different species in this group, like pachaoi and bridgesii, the chloroplasts are going to be inherited by the seeds from the mother plant that bears them. This thows the data off.

T bridgesii is listed in the paper as having a chloroplast DNA sequence that appears ancestral to the clade, but because of the inheritance patterns this result can be questioned strongly.

if I use pachanoi pollen on a bridgesii, then the offspring will have the chloroplast DNA of the bridgesii, the reverse cross has the DNA of the pachanoi. Because of the way the plants in this genera can cross, we need chromosomal DNA analysis combined with chloroplast DNA sequences to generate useful data. The authors do not appear to aknowledge that these plants can cross and when their ranges overlap they do, interspecific hybrids are known to occur in the wild in this genera!!

Evidently bridgesii was such an issue with regard to this that the authors included it in figures 1 and 2, but omitted it from figure 3. Figure 1 is a chart made from morphological data (I consider this a joke), figure 2 is another chart made from the chloroplast DNA sequences (again deeply flawed due to inheritance patterns and cross compatability) however figure 3 is a hybrid made from the two previous figures and data. In figure 1 bridgesii is associated with pachanoi and peruvianus, in figure 2 it is ancestral to the entire clade! in figure 3 it is missing entirely.

There are many issues with this paper and I consider it totally inconclusive and even potentially misleading. The paper even includes two synonyms of the same species as distinct, see if you can spot them. They are morphologically distinct and due to inheritance patternd could have distinct DNA sequences for chloroplasts, but that does not mean they are distinct species.

There are other issues with the paper concerning method, collection and location data etc.

I find it to be a joke.

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cheers for the link. got lots of research on the cards to do today. hopefully get back to you with a few words.

so glad i logged on this morning :)

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Including hybrids in the sample is going to throw out a nuclear DNA analysis as much as it does a chloroplast analysis... unless you've got both.

Good molecular taxonomy should avoid including any samples of potential hybrid origin. If this is achieved then chloroplast DNA reflects pure maternal lineages within species. So the rigour of this study all comes down to what's represented in the sample.

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Including hybrids in the sample is going to throw out a nuclear DNA analysis as much as it does a chloroplast analysis... unless you've got both.

Good molecular taxonomy should avoid including any samples of potential hybrid origin. If this is achieved then chloroplast DNA reflects pure maternal lineages within species. So the rigour of this study all comes down to what's represented in the sample.

 

This is true, however the view that populations only diverge is totally false. Some populations in the cactus family, and in the BTC clade appear to originate as intermediates or hybrids between other species.

This reality totally undermines this type of paper as well as any singular data. Nuclear DNA and chloroplast DNA are needed to generate good data. That is part of why I think the above paper is worse than worthless.

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[edited by kt]

Edited by trucha

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I tend to think it offbase to fault other peoples work for not being designed on the basis of our beliefs. Taxonomists work only with what they consider to fall within the concept of species not hybrids (not as a trend but as a rule).

I ran your thoughts by several botanists and the most pertinent point I heard back, concerning what was dubbed a "preoccupation with hybrids", was: "WE WOULD HAVE TO ABANDON THE NOTION THAT WE CAN EVEN TALK ABOUT SPECIES, SINCE ALL CACTI WOULD HAVE TO BE CONSIDERED HYBRIDS OF NONCONSPECIFIC PARENTS THAT WOULD LIKEWISE BE HYBRIDS OF THEIR NONCONSPECIFIC PARENTS"

At what point does that concept cease to be useful?

Edited by trucha
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And yet the (potential) existence of intermediate populations that gain species status totally undermines relationship values for genetic and morphological data.

it is wise to ignore this and just pretend that the data is meaningful?

It seems like really bad science to not gather enough data to consider this carfully.

Somatic DNA alone, nuclear DNA alone and Morphological data alone are all incapable of dealing with this.

I disagree that all cacti can be considered hybrids of non-conspecific hybrids.

That seems absurd.

Edited by AlbertKLloyd
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[edited]

Edited by trucha
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Hi Albert, Can you please give further information and sources for your comment: "Secondly reports of persistent adverse effects have been known from some clones when consumed raw, this is not well understood but it might not be wise to ingest raw cactus, or at least it might lead to greater risk of negative side effects."
I would greatly appreciate it.
Thanks, Rob

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Hey Rob.

Albert hasn't logged in for over 2 years so I doubt he'll be answering your question particularly soon. (and I can't see where he's written what you've quoted, but that doesn't really matter).

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