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

[John Grehan]

I don't 'object' to fossils as obviously I have used fossils in my biogeographic studies. But fossils can be problematic with respect to identification, sometimes because of shoddy systematics, sometimes because there is just too little material to provide the diagnostic features that would allow their relationship with living taxa to be identified with confidence (e.g. whether Orrorin is more closely related to humans or the orangutan).

In addition, if the morphology of living taxa is supposed to give the completely wrong answer, then there is no scientific way to identify fossil relatives because the morphology of the group is already rendered erroneous. This is the problem with human-great ape relationships, where the morphology consistently links living and fossil hominids with orangutans, but according to molecular theory this is supposed to be completely wrong so one has no integrated method for linking any fossils (i.e. true fossils that lack original organic based material) with living taxa based on morphology (which it would have to), let alone identify a hominid in the fossil record for example.

When you say 'your' biogeographic hypotheses are sometimes proven wrong by ugly facts I presume that this is just a general statement of principle, not referring to specific instances, or is it?

Yes organisms can move around. This is clearly recognized in panbiogeography which you should know if you have read the panbiogeographic literature.

More inserted below

-----Original Message-----
From: taxacom-bounces at mailman.nhm.ku.edu [mailto:taxacom-bounces at mailman.nhm.ku.edu] On Behalf Of Jason Mate


> "Panbiogeography, in its essence, doesn´t use phylogenetic/cladistic 
> information (maybe you´d prefer to call it misinformation ;) ).

This is silly. Why would I prefer to call phylogeny/cladistic information "misinformation" when I have not only used it, but also argued for it (cladistics). 

 Apparently 
> you find this statement untrue, but as practitioners have explained over 
> an over again, tracks are basically a cartographic method of connect-the-
> dots, which then you sort into matching patterns to prove the existence of 
> ancient communities that have been moved apart by vicariance events of one 
> sort or another. Yes, you acknowledge the importance of phylogeny but you 
> don´t use the relationships to determine if your tracks are actually 
> joined in this way or that (i.e. does the sequence match known geologic 
> events) or the timing (before or after) or even if you are comparing like 
> for like (biogeographical homology). 

This is one of those sort of myths that once created, hang around for decades and decades (perhaps I should create a sort of "mythbusters" website on panbiogeography) Phylogeny gives biological relationships. It cannot give spatial relationships. Tracks identify spatial relationships. However, tracks are not constructed in isolation of phylogeny, but with reference to given taxa (i.e. one has a phylogeny) and it is very clearly stated that one can draw tracks first for the lowest taxonomic units (e.g. species, and then sequentially between the higher taxonomic levels. I have called this technique 'vicariance analysis' and given examples in the Brazil chapter.

True, one does not correlate tracks with geological events since the latter are historical theories. One must first correlate tracks with tectonics and from that one has a basis for suggesting the track is linked to the history of those tectonics. A simple example is where a taxon is found either side of a transform fault, but disjunct from each other at distances that match past fault movement. This correlation would suggest the ancestor originated at a time when the fault positions the disjuncts together. When this is found for many taxa of various ecologies the conclusion of a historical relationship becomes even more apparent. One could deny it of course.

> Furthermore you state that this method can predict the existence of 
> previously unknown geological events. Does that mean that your tracks stay 
> in some sort of biogeographical suspended animation until a matching 
> geological event is found? 

This is silly. Panbiogeographic tracks do not all have to represent unknown geological events. The point is that they can lead to the prediction of geological features or events that were not already apparent to geologists.

i.e. you can prove but not disprove 
> panbiogeographical tracks? Neat. That is what I meant by saying that you 
> subordinate patterns to evidence. If what I have said is false then show 
> me an example.

This is getting silly, making assertions without referring to the literature as if something to the contrary does not exist. Craw has given examples of how to 'disprove' panbiogeographic tracks (in the sense of identifying tracks that may not corroborate a standard pattern and therefore be explained by some other event such as dispersal).

Also, one may have a 'false' track if the group it is based on is found to be 'false' (i.e. taxa were determined to be incorrectly linked), but for any given phylogeny there is a given track as an empirical reality since all taxa have a distribution and it can be independently identified just as their spatial relationships are also apparent (and rendered visible by the track).

> If you want to argue about the finer points of biological philosophy, 
> great. But please don´t draw a fictitious line in the sand between 
> dispersal and vicariance. 

Maybe a mirror is in order?

> We all know things can stay put or disperse or become extinct and, as 
> Robin has pointed put in a rather amusing way, the world is a big casino 
> and sometimes the same number can come up 10 times in a row. Describing 
> the the pattern of numbers that comes out of the roulette can be fun or 
> even instructive but it will not help you win when you place that bet.

Well, panbiogeography works so you will have to learn to cope with that reality!

John Grehan

Good night

Jason

 		 	   		  
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