Locality data

Jim McKenney jamesamckenney@verizon.net
Wed, 31 Oct 2012 08:49:55 PDT
Jim Shields wrote: " the DNA sequence of the organism IS the organism, so the DNA sequence perforce defines the species. "

In the biological species concept, it isn't the organism which defines the species, it's the shared gene pool. What the DNA sequence defines is something comparable to the old, pre-genetics species defined by morphology.  DNA sequences do not define species; rather, they are a consequence of the existence of species. In calling them a consequence, what I mean is that their (the DNA sequences') significant grouping is a consequence of the composition of the gene pool, not simply the result of statistical or biochemical analysis. 

Nhu wrote:  However, taxonomy has been pretty good at *recognizing* species. Whatwe humans recognize as species does not make something a species, but it
has its practical purposes."

Isn't that another way of saying that  taxonomy is good at recognizing entities which have practical purposes? The main objection to the biological species concept seems to be  that it is not very practical. We want things to be easy and useful, don't we? 

And Nhu also wrote "  "It only works with organisms that mate, andthere is a huge diversity out there that don't mate, and there are a number
of other species concepts that are used to recognize the asexual organisms."

That some forms of life do not seem to fit into the biological species concept is not a shortcoming of the concept, it simply indicates that not all forms of life exist as species. 

Jim McKenney 

 From: J.E. Shields <jshields@indy.net>
To: Pacific Bulb Society <pbs@lists.ibiblio.org> 
Sent: Wednesday, October 31, 2012 7:37 AM
Subject: Re: [pbs] Locality data
This is indeed a fascinating topic.  From my perspective as a biochemist, 
the DNA sequence of the organism IS the organism, so the DNA sequence 
perforce defines the species.  Geography and morphology are just 
approximations of the species.

I'm not sure how deeply this notion has permeated the rest of biology from 
the molecular biological side, but it is inevitably the direction things 
are going to go.  Until DNA sequencing becomes routine (i.e., a block box) 
and really cheap, we are stuck with morphology and to a secondary extent, 

Operationally, the weakness in the biological species concept is that we 
can rarely if ever actually define the "breeding population."  It is not 
really definable (in terms of "do this then this and you define the 
breeding population" using any doable steps) so it is not really a 
scientific concept.

Jim Shields

At 08:39 PM 10/30/2012 -0700, Nhu wrote:
>This is such a juicy subject that I have to join (just for a little).
>It's always good remember that no one knows what a species truly is.
>Taxonomy and the latest and fanciest science could not yet tell us that
>yet. However, taxonomy has been pretty good at *recognizing* species. What
>we humans recognize as species does not make something a species, but it
>has its practical purposes.

Jim Shields             USDA Zone 5
P.O. Box 92              WWW:    http://www.shieldsgardens.com/
Westfield, Indiana 46074, USA
Lat. 40° 02.8' N, Long. 086° 06.6' W

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