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RE: Livezey and Zusi's paper plagued with convergence?



Mickey Mortimer wrote:

> Now that I have the data matrix, we can see where these large flightless 
> birds end up according to their data.

> All three form a clade sister to Aptornis (another large extinct ground bird) 
> in Gruiformes. Seems somewhat

> suspicious to me. Dromornithids are supposed to be related to anseriforms, 
> Sylviornis to galliforms, and

> Gastornis to anseriforms or maybe gruiforms. Are even huge, detailed 
> morphological analyses just doomed to

> convergence?



Can I take it that you re-did the analysis with these taxa (Dromornithiformes, 
Diatrymiformes, _Sylviornis_) included?


Firstly, I'd be curious about *which* exact characters are uniting these taxa 
with _Aptornis_ inside Gruiformes.  Are they 
necessarily characters associated with large body size and/or secondary 
flightlessness?  (My guess the answer is probably "Yes 
of course they are, stupid".)  The thing is, if they are it doesn't necessarily 
rule these characters out as phylogenetically 
significant.  For example, when Mayr (2004)'s analysis recovered plotopterids 
(extinct wing-propelled divers) as the sister group 
to penguins, he bit the bullet and suggested that it wasn't just convergence 
(homoplasy) pulling them together, but that this 
plotopterid-penguin relationship might be real.  My point is that when an 
analysis recovers taxa in new and unexpected 
positions, it may not be the analysis that's at fault; it may be our 
expectations.  I know Mickey is as familiar with this as 
anybody.  :-)  


Secondly, does inclusion of these oddball taxa (Dromornithiformes, 
Diatrymiformes, _Sylviornis_) lower the bootstrap value for 
a monophyletic Gruiformes?  In other words, is Gruiformes the problem here, 
rather than the oddball taxa?


Thirdly, the phylogenetic affinities of many large flightless birds are highly 
uncertain.  For example, although _Aptornis_ is 
usually regarded as a gruiform, another view holds that it is actually a member 
of the Galloanserae (Weber and Hesse, 1995; 
Courier Forschungsinstitut Senckenberg 181: 292-301).  Dromornithiformes and 
Diatrymiformes are thought to hover 
somewhere in or near the Galloanserae, but I'm not aware if this has been 
rigorously phylogenetically tested yet.  However, 
AFAIK _Sylviornis_ is always allied with galliforms (especially megapodes), so 
it's weird that it pops up in the Gruiformes; but 
again, has this actually been tested?

Of course, what we need is more basal taxa (basal dromornithids, basal 
gastornithids, etc), but they could be a long time coming.


David Marjanovic wrote:

> Or maybe they just contain a few hundred correlated characters. Figuring that 
> out would make a nice Ph.D. thesis or three. 


Nice idea. Why don't you give it a try it in your spare time?  :-)



Cheers

Tim
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