Molecular taxonomy: on way out?
Richard.Zander at MOBOT.ORG
Richard.Zander at MOBOT.ORG
Sat Jul 16 15:26:03 CDT 2005
Molecular taxonomy will be old hat sooner than you think. And the leading
expositor on Taxacom for a new and better way to evaluate evolutionary
patterns as they may be used in taxonomy in the future is . . . (wait for
it). . . John Grehan.
In my opinion, John got to the right conclusion with metaphysical premises.
We, rightly, disagreed with Grehan's "molecular drive" and other
generalizations as an alternative to modern molecular systematics. I've been
looking, however, in the evo-devo literature recently, and in fact there is
some (not much, but some) evidence that evolution commonly involves large
gene complexes regulated (e.g. turned off and on) by non-coding regulatory
genes. This makes for a sloppy evolutionary tree because the silenced gene
complexes can travel the lineage byways for up to 10 million years before
The problem is that some major morphological complexes are greatly split by
molecular systematics. Although statistically the molecular split is well
supported, that split statistically contravenes Dollo's Law that it is not
to be expected by chance alone that two taxa sharing many complex
morphological characters should separately exactly re-evolve (by gradual
accumulation of traits).
Molecular systematics, in my opinion, tracks reproductive splits assuming a
Biological Species Concept (iffy for plants), which mainly also reflects
evolutionary changes (to the extent it matches expectations from
morphological analysis), but instances of apparent massive homoplasy can be
mediated by identical or little changed shared gene complexes turned on by
selection on regulatory genes. It is the only explanation of such homoplasy,
it is not mystical, and it builds on Darwinian thinking.
The human-chimp relationship is statistically supported by molecular studies
as a sister group, but we share too many critical morphological traits with
the patristically more distant orangutan not to suspect some kind or degree
of direct shared genetic past, a deep homology.
If demonstrably shared evolution is more important to systematics and
classification than tree-like segregation of gradually accumulated changes
in introns and junk DNA, and if evolution may not be recovered in at least
some salient cases by molecular systematics, then careful examination of
morphology is a major clue to evolutionary relationships. So, dust off your
1970's phenetic analysis software! Morphology will rule again!
Richard H. Zander
Bryology Group, Missouri Botanical Garden
PO Box 299, St. Louis, MO 63166-0299 USA
richard.zander at mobot.org <mailto:richard.zander at mobot.org>
Voice: 314-577-5180; Fax: 314-577-9595
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4344 Shaw Blvd.
St. Louis, MO 63110 USA
From: Robin Leech [mailto:releech at TELUSPLANET.NET]
Sent: Friday, July 15, 2005 1:37 PM
To: TAXACOM at LISTSERV.NHM.KU.EDU
Subject: Re: [TAXACOM] Insect patronym auction (>$10,000)
If the SYSTEM found it hard to keep, finance and/or justify alpha
and beta taxonomists, how long can it keep on financing and justifying
molecular taxonomists who, for the most part, are not solving problems
at the higher taxa levels, but most often at the genus and species level?
It takes a great deal of money to keep a molecular biologist in equipment,
and upgrades of equipment, in first-class space to keep all this equipment,
and a fair degree of high maintenance of all the equipment.
I guess my main question is this: how much longer will this molecular fad
continue until the common sense of alpha and beta taxonomists returns to
the funding agencies?
Recently, as an associate editor of The Canadian Entomologist, I had the
surprise of finding that taxonomists whom I have known for years could
not deal with a manuscript sent to us. We sent the MS to two people,
neither of whom i a beetle taxonomist, but both of whom are molecular
taxonomists. Apparently it is the analytical process that has to stand up.
In my mind, I could not help but compare the molecular biology approach
to that of numerical taxonomy (Sokal and Sneath) of the early 60s. Will
molecular taxonomy go the same route as numerical taxonomy?
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