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likelihood (?) inference from phylo. distribution

Doug Eernisse DEernisse at fullerton.edu
Sun Mar 10 03:04:43 EST 1996

In article <4hnq4n$80e at News.Dal.Ca>, Arlin Stoltzfus <arlin at is.dal.ca> wrote:

> For instance, C-to-U pan-editing is restricted to angiosperm
> mitochondria. In a review on this type of editing a few years ago, some
> colleagues made what seemed to me to be a fair and obvious statement to
> the effect that the proposal of an ancient origin could not be
> excluded, but was not supported by any evidence.  One of the referees
> objected strongly, saying that this was needlessly offensive to the
> fine people who proposed an ancient origin, since the same status also
> applied to a recent-origin explanation-- theoretically possible but
> without evidence.  Apparently, the referee felt that the phylogenetic
> distribution was irrelevant and was NOT unfavorable to an ancient
> origin of C-to-U pan-editing followed by loss in genomes other than
> those of angiosperm mitochondria.
> I have seen a similar difference of opinion in other contexts.  My
intuition suggests that 
> the referee's view is wrong, but I have not seen
> a rigorous and valid general argument against it.

If this were the only character you are willing to bring into
the discussion then, no, there is no strong argument against it.
If you are willing to bring the currently available evidence
for plant mtDNA as a taxon in the tree of life then, yes, it
would be unparsimonious to advocate that the tree of life
is rooted with plant mtDNA. Such a claim would be necessary in order
to claim the state "C-to-U pan-editing" as plesiomorphic rather than

The same is true for a state uniquely possessed by any terminal
taxon "A" for which there is evidence for (D, (C, (B, A))) and
also evidence that this clade (A-D) does not include life's ancestor.

Doug Eernisse <DEernisse at fullerton.edu>
Dept. Biological Science MH282
California State University
Fullerton, CA 92634

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