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 an
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, but
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). Secondly,
the reason for having an identical COI sequence could be manifold, and could
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 species
can still be viable and valid species despite that finding! (A similar case
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 each
case, a split or lump requires subsequent follow-up studies to corroborate
the case.
Cheers
Frank
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" species
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 this
be the case?
Please excuse the ignorance but I would love someone to explain in simple
terms.....
<>
< DNA splits >
http://www.eurekalert.org/multimedia/pub/3183.php?from=90533
Unique DNA barcodes for provisional new bird species were obtained from
these look-alike specimens.
< DNA lumps>
http://www.eurekalert.org/multimedia/pub/3185.php?from=90533
These groups of bird species were shown to have virtually identical DNA.
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