Biogeographic memory

[P.Hovenkamp]

At 12:43 PM 9/3/01 -0400, you wrote:
(...)
>Here I think the difference in perspective concerns what is a 'phylogeny.'
>In my perspective a phylogeny is the evolutionary history of lineages.
>Lineages have a biological and spatial history. A phylogeny that is
>rendered simply as a set of biological relationships without incorporation
>of spatial relationships is, to my mind, only a partial representation of
>the phylogeny. A natural classification to my mind is one which is
>cognizant of both biological and spatial relationships.

One of the reasons why I find Panbiogeography difficult to understand may
be that it uses a lot of terms in a sense that is distinctly different from
common usage. Thus,  Panbiogeography builds a "parallel universe'  of
terms, which is hardly accessible from this one.
Thus, "dispersal" does not mean dispersal, and "tracks" are not tracks,
"homology" is not homology (not quite, at least), "center of origin" is not
center of origin (or is it?), "main massing" need not be main nor massing
(see p. 79, where a single occurrence in the Comoros is treated as a "main
massing"),  and now "phylogeny" turns out to be not phylogeny (but note how
in the examples of Ch. 4 the term phylogeny seems to be used in its
conventional meaning). I realize that such terminological confusion is
inherent in the establishment of any new research program, but I would have
expected a more coherent account of these terms in a book of this kind,
summarizing 40 years of research after the first establishment of its
research program.

(...)
>>Moreover, and pehaps more telling, Craw, Grehan and Heads give a great
>>many examples and illustrations, but only a very small minority of these
>>refer to explicit hypotheses about phylogeny. Most of this minority is
>>taken up by examples in Ch. 4, and deal with the prediction of
>>phylogenetic relations from biogeographic patterns. Phylogenetic data as
>>input for biogeographic analysis is obviously not what the book is about.
>
>Agreed, phylogenetic (biological) relationships is not the central theme of
>the book.
Here our ways part...

>>Would not that be enough to dismiss the claim that "their distiributions
>>are not distinguishable according to their different means of dispersal"?
>
>Not in my view.

Again - how different must two patterns be to be distinguishable? My
earlier question about this was ignored by John Grehan. I see a lot of
light between Mayr's statement that different dispersal abilities result in
totally different distribution patterns (did he really make such a
catergorical statement? I do not have the reference at hand) and Grehan's
position which seems to be that there can never be an objective criterion
to distinguish such patterns.

>>Perhaps this illustrates the rather arbitrary way in which Panbiogeography
>>uses "similarity".
>>Thus, the two distributions discussed here are treated as "similar",
>>despite clear dissimilarities - as in other cases tracks treated as
>>similar "Indian Ocean Baselines" can be as dissimilar as fig. 2-2
>>(connecting India to Sumatra), 3-3 b (connecting Cape to S. Australia) or
>>3-6  c (connecting Madagascar and India).
>
>Since similarity of distribution range is not part of panbiogeographic
>method

But similarity in baselines is. How is it possible to assign "the same"
baseline to different tracks if there is no notion of similarity? And that
similarity is decidedly arbitrary.

>the illustration of similar in the examples does not characterize
>the way 'panbiogeography' uses similarity.

?

>Perhaps I should have asked Mayr
>to illustrate his original assertions of 'totally' different distributions
>(assuming he would have bothered to respond) and used his criteria for
>illustrative purposes. Problems of similarity aside, the point remains that
>dispersal ability is not a predictor of biogeographic homology.

Is "biogeographic homology" the same as geographical similarity? If not,
this remark seems to be beside the original point.
Anyway, I never intended to question the obvious discrepancies between
obvious means of dispersal and sizes of distribution areas -merely the
choice of the example in fig. 1-1, which I still think does not illustrate
the point very clearly.
(...)

>It would depend on what one is looking for in the way of a summary. A
>graphic summary is provided in Croizat's (1958) global map of dispersal for
>example.

But I asked for a summary of Croizat (1968), optionally incorporating the
data that have become available since.


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