Biogeographic memory

[John Grehan]

>>
>>There was more discussion of phylogeny in Craw's earlier work, but then
>>whether that's 'enough' for anyone I leave to individual preference.
>If it was there, why not deal with it in the book? By downplaying the role
>of phylogeny in the book you apparently left out an essential element of
>the method...

No, as the spatial relationships were the subject of the method the main
massings were sufficient to illustrate the contrast with Nothofagus. The
'phylogeny' (as biological relationships) only gives the biological
relationships anyway.


>>>In this case - a scheme in which only four baselines are allowed.
>>>If a track is not Atlantic, Pacific or Southern - well, then it must be
>>>Indian Ocean.
>>
>>These, along with the Northern and Southern oceans are the four major
>>tectonic basins so if one
>>is interested in the spatial relationships of distributions to those basins
>>then that's the
>>baseline reference. It does not preclude others
>
>The way you arrive at an Indian Ocean baseline by eliminating 3 other
>options is valid only if other options are precluded.

Agreed. I was only saying that others (I should have said five) were not
precluded as possibilities. Of course only one is selected as a result of
analysis.


>>>This way one runs the risk of ignoring the evidence (plainly there in the
>>>examples) that there are different general patterns crossing the Indian
>>>Ocean basis in different ways.
>>
>>Of course, and these can be recognized as different standard tracks with
>>overlapping or nested
>>localities - still within a common baseline with respect to a particular
>>ocean basin. Even Croizat's (1958)
>>map shows different tracks across common ocean basins.
>
>Exactly. So why restrict your interest to only 4 ocean basins?

Actually there are five according to the scheme of Craw. If one is
interested in ocean basin relationships this is the numerical limit. If one
is interested in greater detail within a particular basin then that is the
focus.


>That under the name Panbiogeography you seem to be advocating an approach
>that is both in method and in general purpose different from what Croizat
>termed panbiogeography.

In what way?

>Thus, on basis of Croizat's panbiogeography, there seem to have been two
>developments: one towards "Panbiogeography" in the sense of Craw, Grehan &
>Heads, the other towards vicariance biogeography, integrating Croizat's
>approach with explicit phylogenetic data. I think the latter is the more
>interesting development.

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.

>I was not trying to "pick on" Croizat - merely trying to explain the
>impopularity of and even downright hostility towards his writings.

What you say doesn't seem to 'explain' anything any more than one might say
that the hostility might stem from the fact that most biogeographers are
Darwinian biogeographers, and the most influential biogeographers of his
day did not appreciate having a detailed and persistent critique of what
they took for granted.

John Grehan