Place in taxonomy

[pierre deleporte]

A 16:24 03/07/2002 +1000, Robert Mesibov wrote :
 >I shake my old head in wonderment, though, when someone
 >says "It's the best possible (a)-(b) match because it's the best possible
 >method and I used it properly." "Best currently available" isn't the same
 >as "best possible," and a method that ignores relevant evidence isn't
 >likely to be current for very long.

Right, but as you stated in your previous message:

 >It seems to me the issue is more methodological than philosophical. Tom
 >knows that there's phylogenetic evidence in spatial information, but he
 >doesn't yet have a good method for extracting that evidence. He shouldn't
 >claim that the evidence doesn't exist!

What is needed is effectively a clear method for (possibly) extracting
historical evidence from distributional data. A decisive methodological
contribution would do just that. Hinting that there may be some others ways
to proceed is nice, but stating precisely how and why is necessary... and
still lacking.

Not that biogeographers, even using phylogenetic information, are
neglecting distributional data. Thay merely integrate this in their
reasoning a non-formal, generally implicit and eclectic way. The recent
post by Ken Kinman in reply to John Grehan is exemplary: Ken, pressed by
questions, explained the geological arguments standing behind his
acceptation of minimal spatial spanning tree as meaningful across Atlantic
rather than across Pacific. Thus, he certainly does not ignore spatial
information in his reasoning.
Now there is a universal, formal proposition for dealing with spatial data:
minimal spanning tracks of Panbiogeography, advocated by John. By Ken
refuses it (as I do) because for him, shortest spatial connection cannot
make universal biogeographic meaning. It depends on the dispersal abilities
of taxa combined with geological information about barriers.

So, eclecticism is the present rule, and could be further explored and
formalized in a series of recommendations for interpretation, which in my
view is not likely to result in a uniform minimum-spanning formalism like
Panbiogeography proposes.

But confronting an independent (tentative) phylogeny with independent
(tentative) biogeographic and geological scenarios IS a way to take total
evidence into account.

Alternatively, integrating all the reasoning in, for instance, the
formalized analysis of a single "data matrix of all relevant evidence" (the
equivalent of "simultaneous analysis of total relevant evidence" in
phylogeny inference) would require a high degree of elaboration of
complementary explanatory models and rules for "weighting" them the right
way, which biogeography is far from ready to achieve in my view. Progress
in approaches of limited scope is a useful first step (Hovenkamp's method
for dealing with barriers and vicariance is exemplary in my view).

Pierre