[Taxacom] Antw:Re: RE dispersal

[John Grehan]

 Ha! I wondered whether or not to wait until someone else jumps to the wrong conclusion. My position is, and still is, that molecular results have no automatic precedence over morphology. That is the fundamental position I hold. 

All I have argued in the list and in the literature is that there are potential methodological and conceptual factors in molecular analysis that can result in erroneous results. 

In the orangutan case the range and extent of morphological similarities with humans make the rhetorical assertion that it must be wrong very problematic - in my opinion, and in this case I lean towards the morphological result.

As Peter is or should be aware, I have used molecular phylogenies in my biogeographic analyses. I agree with Mike that molecular studies render biogeographically informative results, which does lead credence to their having some validity. When working with biogeography I used phylogenies as they are presented - whether morphological or molecular, with the caveat that either may be problematic - but one cannot individually study to death every group.

As Mike points out, where incongruence occurs, it may be with one set of characters, but not another. In morphology one is in a position to individually re-evaluate proposed homologies, but there is not the same potential in molecular analysis.

In some cases the molecular-morphological incongruence may not matter so much biogeographically. Take the case of the tarsier. Some (majority maybe - I forget) molecular results support tarsiers being the sister group of anthropoids. The cladistic morphology supports tarsiers being either the sister group of lorises, or even perhaps a member of the Lorisidae. The morphology would tie the tarsiers in more directly with the African-Asian lorisids, but it would seem to change nothing much regarding the biogeographic position of the tarsiers overall.

John Grehan

-----Original Message-----
From: taxacom-bounces at mailman.nhm.ku.edu [mailto:taxacom-bounces at mailman.nhm.ku.edu] On Behalf Of P.H. HOVENKAMP
Sent: Sunday, October 23, 2011 12:49 PM
To: Michael Heads; Jason Mate
Cc: taxacom at mailman.nhm.ku.edu
Subject: [Taxacom] Antw:Re: RE dispersal

For one thing, it appears to tell us that molecular stuff is informative about the past.

Notwithstanding John Grehan's frequent assertions...;-)

Best,

Peter Hovenkamp

Op 22/10/11, Michael Heads  <michael.heads at yahoo.com> schreef: 

> Hi Jason,
> ?
> When?molecular phylogenies started appearing no-one knew what 
> morphological characters, if any,?would agree with them. Would it be 
> tradional 'good' characters, such as 'flowers' in angiosperms or 
> genitalia in insects? Microscopic characters? Chemical characters? 
> Behavioral characters? In fact, variation in a lot of 'good' 
> characters?turned out not to agree with the molecular phylogenies, 
> while characters that were previously regarded as superficial (colour in birds, vegetative differences in plants?etc.) sometimes?tracked the molecular topologies quite well.?But?one character?has turned out to have a special significance across all?the molecular work:?geographic distribution. (It even proved?to be important?in groups such as freshwater plankton and marine groups with planktonic larvae). Just two recent examples: a group of Opiliones in which 'geography is better than taxonomy [i.e. morphological homologies] in predicting phylogeny' (Hedin et al., 2011 Mol. Phylogen. Evol), and the plant genus Mimosa, in which 'Clade W is taxonomically disparate and is better defined by its geographical distribution restricted to the Andes than any obvious morphological or classificatory coherence'(Simon et al., 2011, Am. J. Bot.).Other studies finding the same result are very common (some are cited in Heads, 2011, Syst. Biol.).
> ?
> No-one to my knowledge has?talked about this as a general phenomenon, 
> seen?across all the?molecular work. No-one expected geography to be 'the character', but?it is one of the clearest results of the whole research program.?Why/how does?the molecular variation show such?unexpected, deep geographic structure? What does this tell us about evolution?
> 
> Michael
> 
> Wellington, New Zealand.
> 
> 
> My papers on biogeography are at: http://tiny.cc/RiUE0
> 
> 
> ________________________________
> From: Jason Mate <jfmate at hotmail.com>
> To: Taxacom <taxacom at mailman.nhm.ku.edu>
> Sent: Saturday, 22 October 2011 9:52 AM
> Subject: [Taxacom] RE dispersal
> 
> 
> Dear Michael, some of the comments need clarification."Accepting a 
> literal reading of the fossil record implies that biogeography is 
> caused by random trans-oceanic dispersal and that any repeated 
> patterns are meaningless.""...but you don't accept biogeographic 
> evidence as it is all caused by chance."Current biogeography is built 
> upon two mechanisms, vicariance and dispersal. From your writings I 
> assume (maybe I?m wrong) that you only truly accept a form of 
> vicariance.? In addition, repeating patterns may or may not indicate 
> vicariance.Repeated dispersal along particular routes can result in 
> patterns. "So why are more and more authors putting distribution maps 
> in their abstracts at Molecular Phylogenetics and Evolution? Are all 
> these simple, clear-cut distributions really just due to chance?" Why 
> bring-up MPE specifically? It is a pretty bizarre comment. Maps are a 
> handy way to convey information, they are not a prelude to 
> track-drawing, so it is no
> ?wonder people use them more."If they are not, this suggests that a 
> literal reading of the fossil record might be misleading."I would add 
> that the notion that the fossil record is completely unreliable, thus 
> essentially eliminating lower limits is misleading as well. Taxa can 
> be and are evaluated not just on their direct fossil evidence but on 
> that of higher or related clades. So, even if the evidence for a group 
> is lacking there is often outgroup fossil evidence that can be brought 
> to bear on the problem.BestJason 
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