DNA based lumps, splits and IDs

To: Birding Aus <>
Subject: DNA based lumps, splits and IDs
From: Andrew Hobbs <>
Date: Fri, 23 Feb 2007 18:05:51 +0900
As a molecular genetecist, I would say that relying on 648 bp of mitochondrial sequence is about as good at distinguishing species as sending out a beginner birder and asking whether they think they represent two species.



Dave Torr wrote:
Thanks Frank - that is very clear. So the publicity is about as justified as
(say) a new fig parrot is?

Seriously I have always had doubts (as a non biologist) about some of this DNA stuff - I attempted to read one paper and the author seemed to be saying that if the difference in the small part of the DNA he had studied was more
than "x" % then he would declare the beasts to be separate species. The
choice of "x" seemed totally arbitrary.

Still - I guess as long as taxonomists can generate new ways of looking at
the world we will never be short of the need to buy new bird books and
update our "life lists"

On 23/02/07, Frank Rheindt <> wrote:

David (and others),

trying to keep it short:

1.) These DNA barcode people are just looking at one single gene (COI),
which happens to be one out of three dozen genes on the mitochondrion (a
tiny cell organelle). In the nucleus of each cell, there are millions and
millions more genes, many of which are responsible for the appearance of
organism. So it all depends on what you really want to do: If you were
looking at a gene that codes for the colour of a duck's wing speculum, you bet there would be huge differences between Blue-winged and Cinnamon Teal.
However, phylogeneticists try to look at neutral genes that don't have
anything to do with what an organism looks like, to avoid circularity.

2.) Barcoding is a nice tool to detect "suspects" for splitting/lumping,
in most cases more phylogenetic work will be necessary to corroborate the
split/lump. For example, let's take the case of those "species with
identical DNA": First of all, never say they have identical DNA, but say
something along the lines of "...they have an identical sequence in their
COI gene..." (which is less than a millionth of their total DNA).
the reason for having an identical COI sequence could be manifold, and
involve things such as ancient hybridization events (during which one
species' COI gene "invaded" that of the other) - this is called
mitochondrial introgression and is fairly common in birds. So those
can still be viable and valid species despite that finding! (A similar
in Australian birds involves White-browed and Masked Woodswallows, which
have identical mitochondrial DNA).

Bottomline: DNA barcoding is a nice tool to whet our appetites, but in
case, a split or lump requires subsequent follow-up studies to corroborate
the case.


>From: "Dave Torr" <>
>To: "L&L Knight" <>
>CC: Birding Aus <>
>Subject: Re: [Birding-Aus] DNA based lumps, splits and IDs
>Date: Fri, 23 Feb 2007 15:30:04 +1100
>Maybe I'm missing something (and I'm no expert on DNA!). The reference on
>"splits" shows a number of what I have always thought of as "good"
>anyway, with no indication of what they have been split from (or what has
>been split from them).
>And the DNA lumps shows Blue-winged Teal and Cinnamon Teal to be 100%
>similar - yet visually at least they are very different...... Since as a
>"layman" I assumed DNA controlled the appearance of an animal how can
>be the case?
>Please excuse the ignorance but I would love someone to explain in simple
>>< DNA splits >
>>Unique DNA barcodes for provisional new bird species were obtained from
>>these look-alike specimens.
>>< DNA lumps>
>>These groups of bird species were shown to have virtually identical DNA.
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