Ken Kinman comments on tracks

[pierre deleporte]

A 11:25 01/07/2002 -0400, John Grehan wrote :
 >Ken Kinman wrote:
 >>
 >> This immediately
 >>made me wonder if Leiopelma really forms a holophyletic group (clade) with
 >>Ascaphus.  And sure enough, when Grehan posted a link to his amphibian maps
 >>(TAXACOM, June 12), the paraphyletic nature of that grouping is shown (with
 >>Leiopelmatidae as a separate family) and that long mid-Pacific tract is
 >>gone.  It would indeed be sad if cladists were to propose long distance
 >>transoceanic dispersal rather than questioning their cladograms in such a
 >>case.
 >
 >This is the possibility of reciprocity between the insights of biological
 >analysis of characters and the consideration of spatial characters.
 >According to some there can be no such reciprocal interplay because it is
'>circular' and the source of all phylogenetic insight comes from biology
 >alone. Others such as Hennig and Rosa apparently thought differently.


The qualification of "circular" for such "reciprocal illuminating" is wrong
in most cases, because there is rarely complete tautology. In my view, the
methodological problems at stake is independence, and possible combination,
of different sources of evidence.

If your interpretation of biological characters is not completely
independent from your interpretation of geological data, you cannot
afterwards pretend to "combine" these two sources of evidence as if they
were independent.

Now, you may perfectly combine biological evidence (phylogeny and locations
of taxa for instance) and independent geological evidence (some history of
continent drift for instance) in order to interpret the historical
biogeography of your taxa, under some explanatory logic (models, in a large
acception of the term).

Here I let the ways of "combining" open to your appreciation. But I don't
remember that Hennig suggested to put characters of spatial location inside
the data matrix of *taxa + inheritable biological traits* in order to infer
the phylogeny. I remember Hennig reasoning in terms of "oriented dispersal"
when a morphocline for some characters fitted to a series of spatially
oriented locations for these taxa. This can be extended from morphocline
for a character to phylogenetic relationships between taxa (which the
morphocline was supposed to fit).

Pierre