molecular phylogeny

Andrew Mitchell MitchellA at NU.AC.ZA
Thu Oct 9 16:53:22 CDT 2003


Okay, I'll bite (albeit at the risk of being labelled a "supporter of
molecular phylogeny" which sounds more like a "supporter of Arnold
Schwarzeneger" rather than an impartial scientist...)

1. I don't follow your line of reasoning that just because a mutation
event is random it shouldn't track speciation events. Simple descent
with modification holds true even here: once a mutation has gone to
fixation (and is now called a "substitution") then it can be passed on
to future generations. no reason why this should be homoplasious. It
sounds as if you are confounding "random" with substitutional
saturation.

2. Outgroup comparison, same as morphology! (although if there is
really NO change then obviously you cannot make a tree at all and you
need to find a more variable region of the genome...)

Andrew Mitchell


------------------------------------------------------------------------
Andrew Mitchell
Senior Lecturer, Molecular Phylogenetics
School of Molecular and Cellular Biosciences
University of Natal
Private Bag X01
Scottsville, 3209
SOUTH AFRICA

Tel:  +27 (0)33 260 5815
Fax: +27 (0)33 260 5462

http://www.nu.ac.za/biogen/mitchell.htm


>>> LISTSERV at LISTSERV.NHM.KU.EDU 03/10/09 07:00:10 >>>
>Date:    Wed, 8 Oct 2003 18:16:32 -0400
>From:    John Grehan <jgrehan at SCIENCEBUFF.ORG>
>Subject: molecular phylogeny
>
>I would be interested in what supporters of molecular phylogeny on
this
>list would say with respect to the following two questions:
>
>1. If non-coding regions of DNA are supposed to be subject to random
>mutational changes why should the genetic patterns between taxa match
the
>phylogenetic sequence of taxageny (or speciation)?
>
>2. How would one deal with the possibility that there has been no
molecular
>evolution at all between species for a group so that all that is
being
>compared are the ancestral states with respect to the species being
>compared and thus get a consistent pattern of molecular relationships
but
>one that has nothing to do with speciation sequences?
>
>I realize that there are answers to these questions, but I have not
come
>across them (or I overlooked them in the literature, or I
misunderstood
>what I was reading).
>
>John Grehan
>

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