[Taxacom] Morphology vs Molecular

[Jason Mate]

>Obviously my results contradict molecular results.
Huh? So molecular studies do not contradict yours but yours contradict theirs? Please explain.

>If its more of the right kind of information. More similarities is fine if, in my opinion, 
they can be shown to be uniquely shared within the in-group.

The definition is a posteriori. If the reanalysis including the extra information renders your
previously homologous character states homoplasious, is this the wrong kind of information?

>On that I happen to disagree. It is my understanding of cladistic methodology is that one 
restricts analysis to those features that are unique to the in-group (or at least so rare in 
the outgroup that one has some confidence in their being derived). To do that one must identify 
which features meet that criterion. The analysis is only to determine which group of relationships 
suggested by those features is best supported.

Ah yes, ye old know thou homology. The problem is that just because two structures are homologous the change might not be (i.e. enamel
in teeth might thin in Orangutan´s because of soft fruit diet but in humans, separately, because of food
processing). Even molecular datasets compare homologues (although there are cases where paralogues have 
been compared by accident; same with non homologous morphological strctures).Your definition is just a 
throwback to preHenningian phylogenetics where "only relevant characters"
are used (the definition being that of the author). The final analysis is just a mere formality.


>Right. That is my point, it could be either way. The assumption has been that the morphological 
results need 'explaining' as if the incongruent molecular results do not.

Please John don´t put words in my mouth. The only objective way to decide which phylogeny best represents
the truth (by definition unknowable) is congruence, congruence not only to one dataset but as many as possible.
Phylogenetics is based on data objectivity (i.e. treating all data as equal) and "parsimony" (greatest explanatory power). 
Your counterargument is to say that molecular data is phenetic (how you got here is anybody´s guess) and that
a unique and intimate knowledge of the characters (read, I have been doing this for years so trust me) trumps any
amount of contradictory data (information that it not of the right kind).

>Unfortunately, working 'for' molecules and morphology is not so
straightforward. Of course morphological inheritance has a molecular
counterpart, but this does not automatically mean that current methods
of counting base similarities is necessarily the best way of capturing
this or any other phylogenetic signal, or better than morphological
evidence. 

John, do you even realise how deeply biased, to the point of obfuscation, you are? Base counting (the molecular equivalent
of reading pig knuckles) versus morphological evidence. The word is data! for both.

>The law of large numbers is invoked, but its just a
theoretical or philosophical principle, and one that was used in the
past by morphologists who tried to argue that the more similarities
included the better the result.
 
Yes, expert knowledge (preferably ones own) should be the standard.

>The present conundrum facing systematists is how to decide between
conflicting base counting similarities and morphological similarities.
If the former is accepted as falsifying the latter then we have a real
problem in hominid evolution where the fossil record shows morphological
relationships that are congruent with morphological relationships among
living taxa. 

I can live with that. I happen to think that cladistics is more than ones own
little plot.

>This would have to be dismissed as phylogenetically
meaningless if the molecular theory of relationship among living taxa is
accepted - and this is what is happening at present, even though the
molecular evidence cannot inform the relationships between fossil taxa,
or between fossils and living taxa.

So if you accept molecular data then you are ignoring paleontological data?!
John, please stop and think carefully about this line because it
is simply an emotional gut reaction seeking support.

Best

Jason

_________________________________________________________________
More than messages–check out the rest of the Windows Live™.
http://www.microsoft.com/windows/windowslive/