Biogeographic memory

[John R. Grehan]

>
>Going back through some earlier posts I found that it was John Grehan who
>came up with this as an example of how phylogeny contributes to the
>identification of a main massing:

OK the review of the ratites in the book does not cover this aspect so one
would have to go to the previous literature. If used the book as the
publication
resource for this I was mistaken. I will have to check back to see how
I referred to phylogeny contributing to a main massing.


>This seems to imply (but I may be reading too much in it) that you
>consider geographic features to have some sort of hierarchical
>relationships. There may be a number of features *within* an the Indian
>Ocean basin, but on a lower level. Each of these is still "part" of the
>Indian Ocean basin.

That may be possible

>To me, the existence of the different patterns across the "Indian Ocean
>basin" suggests that this is not a unitary feature, but an combination of
>two (perhaps more) features that are (at least at present) adjacent to
>each other.

That also may be possible


>As far as I understand Croizat, he looked at the distribution patterns
>first, second and third. Only when he had established general patterns he
>started looking for geological or geographic correlates. But he could be
>quite content if he did not find one.

Agreed

>I know there must be a quotation somewhere to back me up on this...
>Perhaps the following will suffice (from Croizat, 1968):
>"The serious student understands, of course, that it is at times very
>difficult, possibly even imprudent under present conditions to effect
>correlations of detail between geology and biogeography (...)"(p. 218)
>"Biogeography, if correctly used, is, in sum, a primary science in its own
>right" (p. 225)

Agreed. So in what way do you regard this as different to the approach I
advocate?



>>In what way is Croizat's approach being 'integrated' with phylogenetic data
>>by vicariance biogeographer - particularly as vicariance biogeography seems
>>to simply be a version of Darwinian biogeography in that it cannot predict
>>biogeographic history without some kind of external (non-biological)
>>criterion. Usually this criterion is concordance with some hypothetical
>>historical sequence from geology or paleogeography - and in this respect is
>>no different from traditional Darwinian biogeography.
>
>A fairly limited view of the developments in vicariance biogeography. Even
>from reading Turner et al. it should be clear that there's more to it than
>that.
>I'm not going to argue whether vicariance biogeography has reached its
>goal or not, but at least this line of approach tries to do two things
>that Craw, Grehan and Heads' Panbiogeographys seems to have given up on:


>1. It considers biological evidence independently from geological data
>(treading in Croizat's steps)

If this 'independence' is the only shared feature with panbigoeography it
seems to me to be little substantiation vicariance biogeography developed
from the method of panbiogeography.

>2. It tries to incorporate the extra detail that resolved phylogenies
>provide, especially with regard to the historical component (an expansion
>of Croizat's method, which has no way to deal with historical information
>of this kind).

Without a homology relationship between biogeography and geology I don't
see how this extra resolution can accomplish anything other than a
non-spatial hierarchical arrangement of areas or taxa.


>They might not have minded so much if every point of criticism would not
>have been accompanied by a sneer.

I never noticed the 'sneer.'

>. Van Steenis first came up with hypothetical "land bridges" (1962) to
>explain the observed regularities in distribution patterns, which nobody
>would believe in.

So had many other biogeographers of his time and before. The question of
Croziat's standing in the scientific community is, I belive, more than a
simplistic appeal to his writing style. One potentially very important
factor I believe is his being outside the North American-European
institutional infrastructure. If he had not been cast out of the Arnold
Arboretum because of political machinations perhaps history might have been
very different.
John Grehan

Frost Entomological Museum
Pennsylvania State University
Department of Entomology
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University Park, PA 16802. USA.

Phone: (814) 863-2865
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