Paul O'Brien wrote:

>Lump the gulls?   Ringler can't get off the hook that easily.   The Barcode 
>paper examined variability in a short segment of the cytochrome c oxidase I 
>gene.   I have seen estimates by geneticists that at least 20 genes must be 
>studied to arrive at any kind of certainty when trying to determine whether two 
>populations represent two separate species.   The CYOI marker is one of the most 
>frequently used, but we need 19 more from other genes.   So don't tear up your 
>old field guides just yet.   
>
>Incidentally, the subspecies pairs cited have been candidates for splitting 
>for quite a while and for other reasons than DNA marker studies.   So keep a 
>lookout for them and you might be banking future full species.   As for the 
>gulls, they obviously don't differ by a whole lot and we shouldn't be surprised to 
>find that they share one gene out of maybe 10 thousand.   Sorry Bob.
>
>Paul O'Brien
>Rockville, Mont. Co., MD
>
>  
>
The bar codes are a good indication, though, even if you might not want 
to treat them as definitive.  The bar code consists of 648 base pairs, 
many of which might vary from species to species and some of which vary 
even inside a single species.  The variation might not change the 
corresponding protein at all, it might not vary the protein in a way 
that changes its function, or it might vary the function in ways that 
improve its fitness under the conditions of the habitat of varying 
species.  The variations that don't change the protein at all are 
especially interesting since they are necessarily not subject to 
selection and so tend to occur in proportion to the amount of time since 
the species involved stopped interbreeding.  If all organisms had 
exactly the same protein, the variation in base pairs would be 
especially useful.

For whatever it may be worth, the web page for the organization which 
will store this data indicates that different species generally differ 
in at least 5% of the base pairs.

The problem is using the data is an old one: how long must two 
populations be separated before they should be regarded as separate 
species?  What is the criterion for separate anyway?

What I find interesting for birdwatchers in this data that has been 
distinctly underemphasized is that the number of potential splits is 
roughly equal to the number of potential lumps.  Have we reached some 
kind of temporary equilibrium in the number of bird species?

-- 
Maurice Barnhill 
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Department of Physics and Astronomy
University of Delaware
Newark, DE 19716