More on Biogeographic memory

P.Hovenkamp Hovenkamp at NHN.LEIDENUNIV.NL
Thu Oct 11 12:58:00 CDT 2001


At 07:50 PM 10/9/01 +0200, Pierre Deleporte wrote:
>Dear all arguing in and following this thread,
>(...)
>The latter point seems to rejoin some way Morrone's allusion to the
>"primary homology" problem in phylogenetic systematics (defining and
>delineating what is a priori a "similar character" in different taxa: the
>"bete noire of phylogenetic inference" according to Pogue and Mickevich
>1990), but in my view this could also be contrasted with the problem of
>delineating terminal taxa in systematics (whose monophyly should be a
>priori asserted, just like the "biogeographical consistence" of areas).

I know this is in fact off-topic, but I can't help pointing out that
monophyly of terminal taxa is a red herring - at least if one applies this
term to species. More inclusive taxa should be monophyletic groups of
species - but one cannot apply the term to the species themselves - for the
perfectly simple reason that one cannot be a monophyletic group of oneself.
But let's continue with biogeography... Although this illustrates how easy
it is to be led astray by easy but inapplicable analogies.

>(...)
>Nevertheless I was striken by the fact that when Craw et al. draw the
>shortest straight line between the distribution of two sister groups,
>Hovenkamp draws a separation between adjacent distribution areas of two
>sister groups. The line or track has to cross the separation or barrier. On
>this limited point, the two approaches look very similar, and this could
>give a handle to contrast them (Peter : why do you draw your line between
>the spatially closest borders of the extension ranges? Or are there
>exceptions to this rule?).

Good question! Come to think of it - the earth being round, it is of course
possible to view any area as being completely surrounded by any other one.
So why the spatially closest border? It somehow seems logical to do it this
way. Perhaps all depends on the scale of the analysis - if sister taxa
occur in close proximity it makes little sense to take the possibility
seriously that they may have vicariated round the world completely - if
they are farther apart, it seems to make little sense to try to measure
whether the one way round is 20000 miles and the other way 19000... In the
latter case, one might want to consider both options.

Peter

P. Hovenkamp
Nationaal Herbarium Nederland - Leiden
PO Box 9514
2300 RA  Leiden
The Netherlands
hovenkamp at nhn.leidenuniv.nl
http://nhncml.leidenuniv.nl/rhb




More information about the Taxacom mailing list