Re: DNA news stories: bird and mammal evolution / GREBE-FLAMINGO

["João S. Lopes Filho" <jodan99@uol.com.br>]

Is there some geographical meaning in this grebe-flamingo hypothesis? Have
grebes a Northern origin? How about flamingos?
----- Original Message -----
From: Toby White <mwhite@houston.rr.com>
To: <bh480@scn.org>; <dinosaur@usc.edu>
Sent: Wednesday, July 04, 2001 5:48 PM
Subject: Re: DNA news stories: bird and mammal evolution


> It could be the reverse just as easily.  I've beaten this issue to death
> before, but a few quick points:
>
> 1) DNA phylogenetics is done on the basis of primary sequence data.  But
> DNA functions either because of its own tertiary structure or the
> tertiary/quaternary of the gene products for which it codes.  Unlike
> morphological data, what you're looking at in sequence data is at least
two
> steps, maybe more, from the business end of selective pressures.
>
> 2) Unlike a lot of morphological studies, where you're not sure whether
the
> assumption of character independence is being violated, you know for
> absolutely sure that its being violated in a DNA study based on one gene.
>
> 3) Even more than morphological characters, bits and pieces of genes get
> shifted around and used in different ways at the same time.  To make a
long
> story short, we don't know whether we're looking at conservation of the
> receptor gene here between grebes & flamingos, or looking at the
> conservation of something else that, unique to grebes (or flamingos), just
> happens to be linked to the sequence of the M6P/IGF2R gene.
>
> Personally (i.e. tiny minority view) I'd like to see molecular
> phylogenetics act more like morphological studies.  Forget the primary
> sequence. Describe the similarities in the shape, charge distribution and
> articulations of the ultimate gene products. Primary sequence studies are
> like trying to compare the meaning of two paragraphs from a statistical
> study of their use of the individual letters of the alphabet.
>
> Go. The rant is ended.
>
> --Toby White
>
> The Vertebrate Notes at:
> http://home.houston.rr.com/vnotes/index.html and
> http://www.dinodata.net
>
>
>
> ----- Original Message -----
> From: <bh480@scn.org>
> To: <dinosaur@usc.edu>
> Sent: Wednesday, July 04, 2001 6:22 AM
> Subject: DNA news stories: bird and mammal evolution
>
>
> > From: Ben Creisler bh480@scn.org
> >
> > DNA news stories: bird and mammal evolution
> >
> > A couple of recent news stories concerning evolution and
> > DNA studies fall a bit outside the topic of dinosaurs
> > strictly speaking but I think they are worth mentioning:
> >
> > DNA yields aquatic bird evolution surprise: flamingo and
> > grebe are close relatives
> > http://www.science.psu.edu/alert/Hedges7-2001.htm
> >
> > If this research holds up, it points out one of the main
> > problems with cladistic analyses based solely
> > on "characters" derived from skeletons -- apparent
> > similarities or dramatic differences in body structure may
> > be misleading in terms of true evolutionary histories. The
> > many birdlike theropods or theropod-like birds that have
> > been turning up lately provide an obvious case in point.
> > Unfortunately without access to ancient DNA, the real
> > story may remain unresolved.
> >
> > (Don't have the citation or abstract for the paper yet.)
> >
> > Mammal evolution theories confirmed and debunked:
> > An article from Popular  Mechanics can be seen at:
> > http://c.moreover.com/click/here.pl?l21352978
> >
> > The official abstract can be viewed at:
> > http://link.springer.de/link/service/journals/00335/bibs/10
> > 12007/10120513.html
> >
> > Killian, J. Keith , Thomas R. Buckley, Niall Stewart,
> > Barry L. Munday, Randy L. Jirtle, 2001.
> > Marsupials and Eutherians reunited: genetic evidence for
> > the Theria hypothesis of mammalian evolution. Mammalian
> > Genome. 12(7): 513-517
> >
> > Abstract
> > The three living monophyletic divisions of Class Mammalia
> > are the Prototheria (monotremes), Metatheria (marsupials),
> > and Eutheria (`placental' mammals). Determining the sister
> > relationships among these three groups is the most
> > fundamental question in mammalian evolution. Phylogenetic
> > comparison of these mammals by either anatomy or
> > mitochondrial DNA has resulted in two conflicting
> > hypotheses, Theria and Marsupionta, and has fueled a
> > ``genes versus morphology'' controversy. We have cloned
> > and analyzed a large nuclear gene, the mannose 6-
> > phosphate/insulin-like growth factor II receptor
> > (M6P/IGF2R), from representatives of all three mammalian
> > groups, including platypus, echidna, opossum, wallaby,
> > hedgehog, mouse, rat, rabbit, cow, pig, bat, tree shrew,
> > colugo, ringtail lemur, and human. Statistical analysis of
> > this nuclear gene unambiguously supports the morphology-
> > based Theria hypothesis that excludes monotremes from a
> > clade of marsupials and eutherians. The M6P/IGF2R was also
> > able to resolve the finer structure of the eutherian
> > mammalian family tree. In particular, our analyses support
> > sister group relationships between lagomorphs and rodents,
> > and between the primates and Dermoptera. Statistical
> > support for the grouping of the hedgehog with Feruungulata
> > and Chiroptera was also strong.
> >
> >
> >
>