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Molecular clock for beginners

Michael E. Zwick mezwick at ucdavis.edu
Thu Jun 15 12:09:00 EST 1995

In article <3rn6dm$4siv at unix1.sncc.lsu.edu>, xxia1 at unix1.sncc.lsu.edu
(Xuhua Xia) wrote:

> John Gillespie has claimed that the residual effect is common. This
> is a serious attack on the foundation of molecular systematics (You
> see that the relationship between molecular systematics and the
> study of molecular evolution is like that of the boat and the
> water. The latter could support the boat, but could also topple the
> boat). In addition to Gillespie, there are also many others who
> attacked the foundation of molecular systematics, sometimes with
> violent words, but few attacks have been based on real
> understanding.

I really think that you overestimate the effects of an imperfect clock on
molecular systematics.  While the molecular clock is clearly not a
"perfect clock", it probably is a good enough empircial generalization for
molecular systematics.  The real issue of John Gillespie's work is
concerned with the maintenance of variation - and in this arena, the
episodic behavior of the clock is of importance in distinguishing between
neutral and selectionist hypotheses.

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