[Taxacom] Poor flying hoatzins dispersed (in flotsam) and orangutangenomes

[John Grehan]

From: taxacom-bounces at mailman.nhm.ku.edu [mailto:taxacom-bounces at mailman.nhm.ku.edu] On Behalf Of Sergio Vargas

Hi there,

> as I see it, the problem with these miracles/unique/rare events is that
> they are not unique/rare at all. 

Not collectively, but for each taxon. The idea is that there is a one off event for a particular taxon so that the 'chance' event results in occupation of an new, isolated location, and the isolation then allows differentiation.


> You have in the literature many examples of Miocene cladogenesis involving 
> trans-Atlantic species pairs in plants and animals, 

I think it would be more probably correct to say that there are many examples of a Miocence origin being asserted.

> and the authors of these papers generally conclude that long-distance 
> (one-off) dispersal was responsible for the colonization of America/Africa 
> using all kinds of means of dispersal to reach either coast. 

Hence 'unique' in each case.

> If taken at face value the Atlantic during the Miocene was covered with 
> all sort of long-distance dispersers using whatever to float around in one 
> direction or the other; it was a high-transit zone! 

There is nothing about this that is face value. Its an assertion.

> I would not call this unique or random, something was going on there, 
> something most have generated the pattern we detect: if not vicariance 
> then dispersal but definitely not random dispersal, there was a process 
> making dispersal easier and this process should identifiable.

Whether something was 'going on' here remains to be seen.

> I tend to see that biologists working with distributional data (not 
> necessarily biogeographers) tend to simply write their speculations about 
> the distribution of a group without been required to justify what their 
> saying. 

Agreed.

> I have reviewed manuscripts telling a biogeographic fairy-tail that is 
> even contradicted by the phylogenies the authors show in their own study! 
> We all need to be careful when we read "the presence of taxon A in area X 
> seem to be the result of long-distance dispersal" and assess if this makes 
> any sense or is simply the biogeographic equivalent of "more data is 
> needed to blah blah blah" (= I have no clue) or "future work should be 
> done to blah blah blah" (=now I have no clue).

Exactly. That is the kind of argument that ken makes.

> I would really like to see how you can generate distributional patterns, 
> congruent among many different taxa, using random dispersal. 

Dispersalists just claim that it happened that way.

> I would expect no congruence at all or at least no more congruence that 
> expected by chance. Dispersal does exist and it is detectable and not 
> random at all. If this one-off random long distance dispersal exist you 
> would not be able to detect it, and if someone postulates that the 
> distribution of a taxon is the product of these unique events reviewer and 
> editors should at least ask him/her to show that there is no other way to 
> explain this distribution a mechanistic process.

Even more to the point is that the means of dispersal have no correlation with the geographic distribution of differentiated entities, but correlations do exist with tectonics.

****

A completely different topic:

> I saw today a presentation on the reconstruction of species trees from 
> gene trees and was a bit surprised by the phylogeny the guy showed 
> including a clade (Orang,(Gorilla,(Chimp,Human))). The reason why I was 
> kind of surprise is because the phylogeny was based on whole genome data. 
> Perhaps I was just wrong but I've kept reading here that the lack of an 
> Orangutan genome precluded whole genome comparisons between Orangs and 
> humans. The Orang genome is available in prepublication form at ensembl, 
> besides Pongo you also have Gorilla, Chimp, Human, Baboon, Gibbon and 
> Macaque. Interesting isn't it.

Whether whole or in part, same kind of analysis, same result.

John Grehan



cheers

sergio



  Dear All,
      Well, I guess I am butting my head up against a Kiwi brick wall, so
won't waste much more time on it.  Anyway, it seems to me that unique
events are automatically rare (by definition), so that argument seems a
semantic distinction of little or no importance to this discussion.  And
besides, we don't know for sure that all such transoceanic dispersals
are actually unique.  Nile crocodiles could have dispersed across the
Atlantic to South America on two or three different occasions for all we
know.  Arguing semantics about unique vs. rare just deflects attention
from more important issues.



On 10/12/11 7:00 PM, taxacom-request at mailman.nhm.ku.edu wrote:
> Date: Wed, 12 Oct 2011 15:42:53 GMT
> From: Kenneth Kinman<kennethkinman at webtv.net>
> Subject: Re: [Taxacom] Poor flying hoatzins dispersed (in flotsam)
> To:taxacom at mailman.nhm.ku.edu
> Message-ID:<COL103-DS2B4E6A755AF77B5A81624A0E30 at phx.gbl>
> Content-Type: text/plain; charset="US-ASCII"
>
> Dear All,
>       Well, I guess I am butting my head up against a Kiwi brick wall, so
> won't waste much more time on it.  Anyway, it seems to me that unique
> events are automatically rare (by definition), so that argument seems a
> semantic distinction of little or no importance to this discussion.  And
> besides, we don't know for sure that all such transoceanic dispersals
> are actually unique.  Nile crocodiles could have dispersed across the
> Atlantic to South America on two or three different occasions for all we
> know.  Arguing semantics about unique vs. rare just deflects attention
> from more important issues.

-- 
Sergio Vargas R., M.Sc.
Dept. of Earth&  Environmental Sciences
Palaeontology&  Geobiology
Ludwig-Maximilians-Universit?t M?nchen
Richard-Wagner-Str. 10
80333 M?nchen
Germany
tel. +49 89 2180 17929
s.vargas at lrz.uni-muenchen.de
sevra at marinemolecularevolution.org

check my webpage:
http://www.marinemolecularevolution.org

check my research ID:
http://www.researcherid.com/rid/A-5678-2011



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