[Taxacom] Hedges /Kumar (eds) The Timetree of Life

[John Grehan]

-----Original Message-----
From: Sergio Vargas [mailto:sevragorgia at gmail.com] 

> nice, yet another assumption free method... how do you identify > what
happened in the absence of a null model? and, if does not 
> assume dispersal or vicariance, could panbiogeography ever 
> conclude that dispersal was responsible for anything?

My reading of Croizat is that he wanted to test whether means of
dispersal was correlated with the geography of distribution. He did not
couch his hypothesis in your terms, but presumably he worked from the
assumption that widespread taxa that spanned major geomorphic formations
(such as ocean basins) would be good dispersers, and that those that did
not would not. So perhaps a null hypothesis would be that good means of
dispersal would be correlated with ocean-basin spanning tracks. If you
are into null hypotheses I am sure you could formulate such criteria.

Dispersal and vicariance can be addressed in panbiogeography, but they
are not the primary problem for the science of  panbiogeography where
the primary problem (and this is just my opinion, others may differ) is
over whether the history of earth and life are correlated, and if so to
what extent.

 >>Which information specifically?
> cladograms, to direct the graphs.

How geographically?


 >Again bizarre stuff. Obviously never even read Craw et al (1999).

> nop, too expensive for me. Do you need a phylogeny to draw a 
> track? I thought you didn't, but I haven't read Craw et al. 
> 1999, my bad.

Well its worse than bad. The content is derived from publications that
would not be out of your reach. A track is defined as a minimal spanning
tree, where localities are linked by the shortest geographic distance IN
THE ABSENCE OF OTHER INFORMATION. As I pointed out in an earlier
posting, one can link individual taxa together first, and then link
related taxa in the order of their relationship (or just their minimal
distance).

As I mentioned in an earlier posting, a beginner paper posted on my
website that covers various approaches although I do not go into
quantitative algorithms as its not my forte.
http://www.sciencebuff.org/research/current-research-activities/john-gre
han/evolutionary-biography/panbiogeographic-publications/grehan-publicat
ions/

 >It does not matter whether [dispersal] its random or not.

> ok, is even simpler: dispersal never ever happened. Getting 
> nervous...

???

> and so? panbiogeographers reject anything else and accept only 
> geography? getting more nervous...

And so panbiogeographers are unique in accepting spatial information as
biogeographic data for biogeographic analysis. All other
non-biogeographic information/predictions may be considered with respect
to the biogeographic data and analysis.

 >Another problem? Oh goody.

well, it is actually a major problem. At least for people using
compatibility to find generalized tracks.

>> Since when is clique analysis the only panbiogeographic method?

> well, it has been used frequently to find generalized tracks, 
> even if it assumes vicariance (and panbiogeography apparently 
> doesn't).

Please cite the publications illustrating the frequent use of clique
analysis.

> I guess, I'll have to read Craw et al. 1999.

No one's forcing you to read anything, but if one wants to critique
panbiogeography (and there is certainly nothing wrong with that) it
would be nice to see the critiques refer to specific applications that
substantiate what may be perceived as problems.

John Grehan

sergio