Punctuated equilibrium and molecular clocks?

Guy A. Hoelzer hoelzer at med.unr.edu
Wed Sep 9 11:43:07 EST 1998

On Wed, 2 Sep 1998 15:16:45, Johnjoe McFadden <j.mcfadden at surrey.ac.uk> wrote:
> Punctuated equilibrium and molecular clocks?
> The punctuated equilibrium hypothesis of Gould and Eldridge, in which
> evolution is proposed to go through long periods of stasis interspersed
> with bursts of rapid evolution, is of course related to the fossil
> record. However, periods of rapid evolution should also leave their
> trace in molecular clocks. 

First, I think that molecular and phenotypic evolution are sufficiently
decoupled that bursts of phenotypic evolution do not need to coincide with
bursts of molecular evolution.  Of course, it is possible that they are
related in some instances and it would be very interesting if this could
be demonstrated.

My colleagues and I have a recent paper discussing punctuated evolution at
the molecular level in which you might be interested.  The paper does not
deal with phenotypic evolution at all.  Rather, it provides the results of
exploring a computer simulation model of mtDNA evolution in a spatially
and socially structured system.  One of the results is that the temporal
pattern of evolutionary substitutions is not one that varies continuously,
as suggested by analytical models of neutral evolution.  Instead, it can
be distinctly punctuated with long periods lacking any substitution.  If
you are interested, the reference is:

Hoelzer, G. A., J. Wallman and D. J. Melnick.  1998.  The effects of
social structure, geographical structure and population size on the
evolution of mitochondrial DNA.  II.  Molecular clocks and the lineage
sorting period.  Journal of Molecular Evolution 47:  21-31.

Guy Hoelzer                              e-mail:  hoelzer at med.unr.edu
Department of Biology                    phone:   702-784-4860
University of Nevada Reno                fax:     702-784-1302
Reno, NV  89557

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