[Taxacom] RE dispersal

[Michael Heads]

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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