Barcoding: sample size

jason at jason at
Thu Feb 6 16:24:32 CST 2003


Richard Zander wrote:


>>Is
>>that what taxonomists do? Identify organisms?
>>
>>I think taxonomists do a lot more. As to money, we taxonomists have 250
>>years of the Linnaean endeavor behind us and have generated or mediated
>>great economic gains for the human race.

Technically yes, that is all that the word taxonomy means. As for the value
of this work, currently it is in the eye of the beholder.


>>_Everybody_ ducks my concerns about the statistical basis behind
>>reliability
>>of phylogenetic estimation.

The aforementoined problems with phylogenetics also affect morphological
and/or any other source of data currently in use. Morphology is by no means
superior or inferior to DNA: each has their place.



Steve Manning wrote:

>Maybe the codes need to be modified to require a sample
>of ten or more specimens, as randomly selected and hopefully as
>ecologically and geographically diverse as possible, to qualify as the
>"type" of a taxon for future species descriptions, unless fewer than ten
>specimens are available.  I acknowledge that it probably won't be easy to
>require broadening the type specimen concept to the point of assuring its
>statistical validity, but nothing ventured nothing gained.

I can think of many reasons why this is a bad idea, but maybe the easiest is
"cryptic species". There is a reason why taxonomy/systematics has moved away
from the type series to the holotype. Granted, variation is not embodied in
the type, but hopefully the researcher had the good sense of looking at more
than one specimen when publishing the description.


>If we ever do get to the point of using Bar Codes or other means of
>categorizing DNA diversity, I hope it can be made essentially mandatory
>that a sample of a statistically valid number of specimens (10?) (100?) and
>gene sequences per specimen (10?) (100?) be included in the DNA analysis in
>order for the analysis to be recognized as valid.

Again, multiple specimens of a species, but how do you know that they are
the same species? And if you do, why do several of them?


>If  the above were implemented, it ought to be able to generate more
>funding for both morphological and molecular taxonomists!


Yes, due to the overwhelming redundancy.


Cheers

Jason F. Mate
4th Fl Entomology
The Natural History Museum
Cromwell Road SW75BD
London, UK



>Steve Manning
>
>>R.Z.
>>______________________
>>Richard H. Zander
>>Bryology Group
>>Missouri Botanical Garden
>>PO Box 299
>>St. Louis, MO 63166-0299
>>richard.zander at mobot.org <mailto:richard.zander at mobot.org>
>>Voice: 314-577-5180
>>
>>
>>
>>-----Original Message-----
>>From: Andrew Mitchell [mailto:MitchellA at NU.AC.ZA]
>>Sent: Tuesday, February 04, 2003 9:18 AM
>>To: TAXACOM at USOBI.ORG
>>Subject: Re: [TAXACOM] Barcoding (animal) life
>>
>>We *sample* taxa not only
>>because of limits of time and money but because of the law of
>>diminishing returns. We want to be able to reliably identify organisms
>>and as an added bonus work out their evolutionary history, not count all
>>stomata on all specimens in the herbarium just for the fun of it.
>>
>>
>>Molecular and morphological/phenological/ecological etc. work can
>>proceed simultaneously.
>>
>> >
>
>Stephen D. Manning, Ph.D.
>Professor of Biology
>Mathematics and Science Division
>Arkansas State University - Beebe
>P. O. Box 1000
>Beebe, Arkansas 72012-1000
>USA
>Tel: 501-882-7162


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