[Taxacom] Geophylogeny (resending)

[John Grehan]

Just an added comment about 'missing data' in biogeography. That's effectively what tracks identify since they provide a minimum spanning link between the known data points with the assumption that those points are disconnected over space by the 'missing data' between them. Perhaps it could be seen as points being the present data, and the graph being the 'missing data' made present.

John Grehan 

-----Original Message-----
From: taxacom-bounces at mailman.nhm.ku.edu [mailto:taxacom-bounces at mailman.nhm.ku.edu] On Behalf Of John Grehan
Sent: Friday, November 12, 2010 4:36 PM
To: taxacom at mailman.nhm.ku.edu
Subject: Re: [Taxacom] Geophylogeny (resending)

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). 
                    --------Ken
----------------------------------------------
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):
741-752. 
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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