Biogeographic memory

[P.Hovenkamp]

At 07:18 AM 9/7/01 -0400, you wrote:
(...)
>Since the meaning of orientation is does not imply dispersal route the
>suggestion that it does would arise only if one wants to treat orientation
>that way.

Add "orientation" to the list I gave earlier...

>No? But compare fig. 3.11 b with fig. 1-10 b and c to see how a
>distribution on both sides of the Pacific can be given a Pacific as well as
>an Indian ocean baseline...
>
>Designation of baselines does involve several considerations and it is
>possible that because there is no spatiotemporally independent criteria the
>procedure may be viewed as arbitrary. Where a distribution is adjacent to
>more than one ocean basin it is not possible to use minimum distance alone.
>In fig 1-10 b and c the distributions were spatially unproblematic.Two
>other contributing elements are main massings and phylogenetic
>relationships. This is discussed in some detail (maybe not enough for some)
>for the ratites.

As a matter of fact - for the ratites the discussion in the text deals with
"main massings" based on numbers of families. Supposing that families are
monophyletic, that does bring in a little phylogeny. Not much.

>Detailed assessment was not applied to the distributions
>so one could argue that their Atlantic/Indian baselines is not sufficiently
>supported in the text.
>
>And to assign the same (Indian ocean) baseline to the tracks displayed in
>fig. 3.3 b and 3.4 seems to me more than a little arbitrary.
>
>The distribution of Pelargonium (3-3 b) is massed around the Indian Ocean
>so an Atlantic or Pacific, or Southern basin could not be applied. The same
>applies to the distributions in 3-4.

This exactly illustrates my misgivings. Panbiogeography (sensu Craw, Grehan
& Heads) refuses to look at the independent evidence provided by organismal
distribution patterns. It attempts to force the multitude of patterns onto
a preconceived scheme based on geography or geology. 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. 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.
As far as I can make out, it is also a long way from Croizat's approach -
Croizat plainly refused to believe anything that was contradicted by the
distribution patterns he observed.

>The comments by Hovenkamp do lead to some useful ideas about improvements
>to the book in the future - particularly issues of clarification (always
>difficult to anticipate). This kind of feedback was particularly difficult
>to obtain in the past as most traditionalists wrote panbiogeography off

Returning the compliment, I'm sure.

>so
>one could not get constructive feedback.
>Panbiogeography is still banned
>from some journals as a matter of editorial policy so even developing
>debate over such issues can be quite restricted in venue.

Croizat's volatile temper and his peculiar style have a lot to answer for.

>However,
>Hovenkamp's comments show, however, that the most detailed critique of a
>work may come from opposing research programs and so ironically 'opponents'
>become ones best allies for improvement.

Memories of something called "repressive tolerance" come back to me....


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