As Cladistics and "Eclecticism", Aves, paraphyly flow on

[Dave Walter]

Hi all,

Apologies to Barry Roth, but he did raise some fundamental questions, so
I'll use that as my excuse to wade into the flood of emails that seem to
represent three parallel torrents (or two torrents and a trickle).  If I
drown, it's my own fault, because I haven't seen any logical log floating
by I'd like to grab on to, no sign at all of a well designed boat, and I
don't swim.

I'll admit that I was first introduced to phylogenetic systematics during
my doctoral research 20 years ago, I've considered myself a 'cladist' ever
since, and I use cladistic methodology by preference - because it's the
best mouse trap around for phylogenetic analysis.  But I draw the line
there - cladistics is a tool, a flawed tool, but better than anything else
I've used.  Since I work on the evolutionary history of mites, I need a
good mouse trap, because mite phylogeny is a mess from the tip to the
base.  However, not since I was a student have I tried to confound
cladograms with taxonomy.  Cladograms represent testable hypotheses and
have provided great insight into the evolutionary history of the Acari, but
I know that even the best cladogram is not the ultimate truth.  So, while I
might rib some friends over their continued use of traditional but probably
paraphyletic groups (e.g. Oribatida, Endeostigmata), I use them myself
because they are well known, hold a lot of  information (even if it isn't
the best available), and maintain stability while a more mature system is
under development.  Maybe this attitude would ban me from any lifeboat
manned by true cladists that swept down this torrent, but since it will
eventually hit the rocks ...

The rocks are pretty obvious, although no one seems to want to look at
them.  For example, we all know (although some insist the contrary) that
evolutionary events are not exclusively dichotomous.  This is a simplifying
assumption that is necessary for the technique to work well, but our
favoured model of speciation (allopatry) could easily generate multiple
simultaneous branching events.  Sympatric speciation may be locally
dichotomous, but is also open to the generation of multiple species from a
single ancestral species (as recent work on frogs demonstrates
nicely).  I've learned that the inherently paraphyletic nature of
speciation events is one of the things that are best not talked about, but
it must make even the most fundamentalist of cladists uneasy.  More
importantly, it is becoming increasingly obvious that reticulate evolution
is important in many, if not most, sexual groups.  Nor are bacteria,
archetypal clones (another problem for cladistics), free from wandering
genes.  Nor are gene trees the same as species trees, and so on.  There are
lots of interesting rapids ahead.

So, maybe the last hundred or so Taxacom emails have just been a lot of
rubber rafters splashing each other for fun, and flexible rafts won't have
any problems on the rocks.  Maybe I'm being a spoil sport, but I think
there are much deeper problems with current systematic theory and
methodology that are worth considering.

Wet knees or going down once?

Cheers,

Dave Walter

At 11:16 AM 3/02/2002 -0800, you wrote:
>  Not so much a reply as a request for clarification:  did the term
> "Eclecticism" (should that be "Eclectism"?  we don't say "Cladisticism")
> exist before its usage in the threads of TAXACOM?  And does it logically
> stand on the same footing as "-isms" like Cladistics, namely, having a
> fundamental group of principles, even though possibly with different
> ideas as to how to implement those principles?  As near as I can tell,
> Eclecticism is more of a mind-set -- a willingness to, as Ken puts it,
> diversify one's portfolio, by picking and choosing from among available
> methods/algorithms (but without one governing principle to guide those
> choices).
>Barry Roth
>
>
>
>---------------------------------
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Dr David Evans Walter
Department of Zoology & Entomology
The University of Queensland
St Lucia, QLD 4072 Australia

phone: 07-3365-1564
fax: (61) 7-3365-1655

The University of Queensland Remote Program in Entomology
http://www.zen.uq.edu.au/remote.php

Cooperative Reseach Centre for Tropical Plant Protection
http://www.tpp.uq.edu.au/

Visit the Mite Image Gallery at:
http://www.uq.edu.au/entomology/mite/mitetxt.html