[Taxacom] very nice opinion article in today's Zootaxa

Paul J. Morris mole at morris.net
Fri Sep 30 15:56:03 CDT 2011


On Fri, 30 Sep 2011 14:39:21 -0600
"Michael A. Ivie" <mivie at montana.edu> wrote:
> Hmm, Rchard, looking through your publications, I do not find one on
> multiple species with a minimum of one thousand specimens per species
> listed in the material studied.  Did I miss it?  I certainly have
> never accomplished that level of specimens in my material studied!
> In fact, I don't think I have ever seen that done.

A quote from Louis Agassiz comes to mind: 

"J'ai pris la peine de comparer entre eux des milliers d'individus de
la même espèce; j'ai poussé dans un cas la minutie jusqu'à placer les
uns à côté des autres 27000 exemplaires d'une même coquille dont les
espèces congénères (le genre Neritina), sont fort voisines les unes des
autres. Je puis affirmer que sur ces 27000 exemplaires, je n'en ai pas
rencontré deux qui fussent parfaitement identiques; mais sur ce grand
nombre je n'en ai pas non plus trouvé un seul qui il déviât du type de
l'espèce au point d'en laisser douteuses les limites." 

"[I have taken the pain of making comparsions among thousands of
individuals of the same species; I was urged to in one case of minutiae
as far as placing one next to the other 27000 copies of the same shell
of which one congeneric species (genus Neritina), is strongly adjacent
to one of the others. I affirm that in these 27000 examples, I did not
encounter two which were perfectly identical; but from this large
number I did not find one single specimen which deviated from the type
of the species to the point of of leaving its boundaries uncertain.]"

Agassiz, L. 1869. De l'Espece et de la Classification en Zoologie.
pp.375-391 Part 3, Chapter 7: Le Darwinisme. - Classification de
Haeckel. Balliere, Paris, 394 pp.

-Paul

> 
> Michael Ivie
> >
> > Compare:
> >
> > A molecular data set of say 50 species, represented each by one
> > exemplar, and 1,000 phylogenetically significant sites gives 50,000
> > data points. This is considered a big data set.
> >
> > But, a morphological data set of 50 species may have each 50 traits
> > represented (over 250 years of study determining trait
> > distributions) by an average of 1000 specimens each, and we get 50
> > x 50 x 1000 = 2,500,000 data points. Say only half the traits were
> > genuinely conservative (resistant to adaptive change) and we get
> > 1,250,000 data points.
> >
> > The difference is that the molecular data set results in a cladogram
> > that does not cluster specimens. The 95% credibility distinguishes
> > single specimens, so one can easily imagine two or more samples
> > occurring in one broad morphological distribution of traits. Just
> > because the two samples differ at 95% or more in credibility is no
> > cause to postulate two cryptic species.
> >
> > Only if the distribution of molecular variation of many samples
> > matches the distribution of morphological variation of many samples
> > is there genuine support of molecular data and morphological data.
> > If there are only small samples of molecular data, any match is
> > mere corroboration ("not incompatible with") not support, for the
> > morphological study. A mismatch means nothing.
> >
> > The burgeoning number of samples per taxon in barcoding is excellent
> > news.
> >
> > * * * * * * * * * * * *
> > Richard H. Zander
> > Missouri Botanical Garden, PO Box 299, St. Louis, MO 63166-0299 USA
> > Web sites: http://www.mobot.org/plantscience/resbot/ and
> > http://www.mobot.org/plantscience/bfna/bfnamenu.htm
> > Modern Evolutionary Systematics Web site:
> > http://www.mobot.org/plantscience/resbot/21EvSy.htm
> >
> >
> > -----Original Message-----
> > From: James Whitfield [mailto:jwhitfie at life.illinois.edu]
> > Sent: Friday, September 16, 2011 5:36 PM
> > To: Richard Zander
> > Cc: Doug Yanega; taxacom at mailman.nhm.ku.edu
> > Subject: Re: [Taxacom] very nice opinion article in today's Zootaxa
> > Not to argue for using only one sample to stand for a species, or
> > only one DNA barcode, as I agree with you that it is a bad idea.
> >
> > But if people would bother to look carefully at the original papers,
> > they are based on LOTS of molecular samples from each species.  It
> > is the CONSISTENCY of the molecular or morphological differences
> > that is critical, not how major the differences are. In this case
> > the molecular and morphological differences are consistent across
> > many samples within putative species and do indeed support one
> > another.
> >
> > Most species descriptions based on morphology (probably 95% + of all
> > species descriptions?) do not have any convincing analysis
> > associated with them. We are in the habit of trusting the experts
> > in this case rather than requiring strong evidence.  Most of the
> > time this works really well, I'd say.
> >
> > Jim
> >
> > _______________________________________________
> >
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> >
> > The Taxacom archive going back to 1992 may be searched with either
> > of these methods:
> >
> > (1) by visiting http://taxacom.markmail.org
> >
> > (2) a Google search specified as:
> > site:mailman.nhm.ku.edu/pipermail/taxacom  your search terms here
> >
> 
> 


-- 
Paul J. Morris
Biodiversity Informatics Manager
Harvard University Herbaria/Museum of Comparative Zoölogy
mole at morris.net  AA3SD  PGP public key available




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