Acarina, pycnogonids, Permian ticks?

John Grehan jrg13 at PSU.EDU
Thu Apr 19 07:45:55 CDT 2001

>Could it be that the foundation for such an assertion is based on:
>- The assumption that in the past, the average range of a taxon was not
>significantly different from what it is now (a position called actualism, I
>believe), so that there must have been many local species, some of which
>inevitably ancestral to current groups?

This is a possibility. I presented it just to indicate that there was an
alternative interpretation possible for the same phylogenetic and
distributional information that is otherwise presented as if it implied
only one possible history.

>- The consideration that speciation is far easier to achieve in small
>isolated populations,

Easier for who?

>and therefore is far more frequent in small "centres
>of origin"

Just because it is an easier 'consideration' does not make it a more
frequent reality.

>Thus, without any distinct evidence to the contrary, the foundation for
>such an assertion may not be analytical (whatever that may be), but
>nevertheless good science.

No analysis but good science?

>Science has to start somewhere, and does not
>progress if one has to argue each starting point from first principles.

I was not suggesting this, although first principles are often presented in
fields where there are contrasting approaches. In the paper referred to
there was a complete lack of information to support the assertions. It
would be like asserting a phylogeny without specifying the synapomorphies.
This is no longer accepted in biological systematics, but for some reason
an exception is made for biogeographic systematics.

>Sorry if I may have missed some important defect in Klompen's reaoning, but
>I do not have the zoological literature at hand.

It does not matter as he didn't present his reasoning anyway.

John Grehan

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