[Taxacom] Geophylogeny (resending)

John Grehan jgrehan at sciencebuff.org
Fri Nov 12 15:36:17 CST 2010

An alternative to Ken's center of origin theory (i.e. Darwin's theory) is that the fossils and living distributions of hummingbirds tell nothing about any speculative 'migrations'. It is possible that the ancestor of humming birds had a range that encompassed both the old and new worlds. In other words, it does not matter where that ancestor 'started out' (it might have started out with a range that was as wide as that of its descendants).

But ken is right about missing data, which is why all one has to go on is what is known (I think that is true of science in general). Even with new fossils the extent of a distribution might be expanded, but in most cases it does not require any change to what was previously understood about the biogeographic pattern.

John Grehan

-----Original Message-----
From: taxacom-bounces at mailman.nhm.ku.edu [mailto:taxacom-bounces at mailman.nhm.ku.edu] On Behalf Of Kenneth Kinman
Sent: Wednesday, November 10, 2010 11:15 PM
To: taxacom at mailman.nhm.ku.edu
Subject: [Taxacom] Geophylogeny (resending)

 Hi Bob, 
        I sent this post on Sunday, but it apparently
didn't go through:  I haven't read the paper, but locating nodes
"centroidally" seems like it could often be too simplistic and very
misleading. Especially given the much longer history of fossil
exploration in certain parts of the world (such as Europe and North
America), but far less in places like Africa or parts of Asia. 
        For instance, before hummingbird fossils were
discovered in Europe, a "centroidal" location for the known living and
fossil hummingbirds would be somewhere in the middle of the Americas. So
with the more recent discoveries of older hummingbirds in Europe, does
that place their ancestor "centroidally" in North America? 
        This ignores the possibility that hummingbirds
actually originated in parts of the Old World that haven't been sampled
nearly as much as Europe. They could have started out somewhere in Asia
and spread eastward through Europe and then the Americas, or they could
have started in North America and spread southward into South America
and eastward into Europe. I don't see how "centroidally" locating a node
would help us much in such cases. When sampling is poor, and especially
when preservation is problematic (hummingbird bird bones are certainly
not robust, so preservation and sampiing are huge problems), things
getting extremely uncertain and any number of different scenarios could
have yielded the presently known distributions. 
      It sort of reminds me of "main massings" in
panbiogeography. It might sometimes work, but when things are not so
simple and straightforward, a "centroidal" approach might not be
appropriate (whether we are taking fossils into account or not). 
Bob Mesibov wrote: 
       An article in the latest issue of Systematic
Biology attempts to address the placelessness of phylogenies by
generating space-time diagrams with explicit procedures: Kidd, D.M.
2010. Geophylogenies and the Map of Life. Systematic Biology 59(6):
If you're interested in this subject, I recommend that you read this
paper critically. Spoiler alert: after a marvellous introduction, the
author chooses to locate nodes at points 'centroidally' intermediate
between locations for the two terminals. This needs work. 


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