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

Michael A. Ivie mivie at montana.edu
Fri Sep 30 15:39:21 CDT 2011


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.

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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-- 
Michael A. Ivie, Ph.D., F.R.E.S.
Montana Entomology Collection
Marsh Labs, Room 50
1901 S. 19th Ave
Montana State University
Bozeman, MT 59717-3020
USA

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