species and speciation

Joe Felsenstein joe at GENETICS.WASHINGTON.EDU
Thu Dec 13 08:05:18 EST 1990


Jim Danoff-Burg writes:

>                    Mitochondrial DNA work may lead to
> misinterpretations of the "truth", since it assumes constant rates of
> speciation (ie: gradualism) and uniform speciation rates.  [I am not
> disparaging mDNA work, only its universal application.  I am sure that
> organisms that have been in a relatively constant environment would be
> most effectively analyzed using mDNA]

I believe that this is a misconception.  I know of no reason to
believe that in making mitochondrial DNA phylogenies we are assuming anything
about rates of speciation or rates of change of morphological characters.
They may or may not assume clocklike change of the molecular sequences,
depending on how the analysis is done, but that can of course happen even as
the morphology behaves in a most unclocklike way.

Perhaps I am missing something -- is it being assumed that the objective
of inferring the phylogeny is to assess morphological rates of change or
estimate the genealogy?

The remainder of the posting is about concepts of speciation.  I suggest
that it be reposted to the population-biology group which is where
that belongs, as it has nothing specific to do with molecular evolution.

-----
Joe Felsenstein, Dept. of Genetics, Univ. of Washington, Seattle, WA 98195
 Internet:         joe at genetics.washington.edu     (IP No. 128.208.128.1)
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