[TN-Bird] Van Remsen nails it

From: James Brooks <comeback@xxxxxxxx>
To: Tenn Birds <tn-bird@xxxxxxxxxxxxx>
Date: Fri, 28 Feb 2003 13:50:29 -0500
I lurk on a couple of ornithological discussion groups, one of which is 
run by Van Remsen at LSU.
There was recently some discussion on James Peters work of 50 years ago 
in which he was the dean of lumping, to which Van Remsen responded with 
a bit of historical background on the lumping-splitting cycle, and then 
expressed concern about the current vogue of using DNA as ultimate 
arbiter of species status, on which he concluded with the following:

"on
the ancient problem of whether two allopatric populations are species
or not, all DNA does is place the degree of difference between the
two on a continuous scale of % sequence divergence, along which no
arbitrary threshold can be defended conceptually as an assay of
species rank, in my opinion."

How nice when one of the finest minds in ornithology can lay out in 
plain English an answer to a question that has been lurking in the minds 
of many of us amateurs for a long time - at what point in the DNA chain 
do we determine whether a new species has evolved?

DNA is useful in determining if gene exchange is taking place, and can 
give an idea of when, historically, gene exchange stopped taking place. 
In this regard we can start to look forward to seeing numerous splits 
taking place between Eurasian and American species. Probably the one 
most talked about just now is into Kentish Plover Charadrius 
alexandrinus and Snowy Plover Charadrius nivosus. Other possibilities 
are Northern Harrier, Common Raven, White-winged Scoter.
Already in Eurasia there is much discussion about splitting European and 
Asian races, so keep track of your wagtail races when you travel!

James Brooks


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[TN-Bird] Van Remsen nails it

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