Re: Evolutionary interplay of caution and boldness in populations

In article <dll6at$1qo3$1@xxxxxxxxxxxxxxxxxxx>,
Gene <stargene@xxxxxxxxxxxxx> wrote:
>It seems to me that the survival of a population and indeed a species
>may often hinge on the complexity or flexibility of its response to
>environmental pressures.
....
>Question: What computer modeling has been done exploring the
>evolutionary/survival value, for an artificial population, of a wide
>range vs. a narrow range of responses, in environments having
>different degrees of complexity and severity in their impacts on
>populations/species?

It is first of all a matter for mathematical modeling, falling back
on computer modeling only when absolutely necessary.

Back in the 1960's (1962 on) Richard Levins had models showing that in cases
like these the mean population fitness can be highest when the population
is polymorphic for two (or more) phenotypes. This is summarized in his
1968 monograph
Levins, R. 1968. Evolution in Changing Environments
Princeton University Press, Princeton, New Jersey.

The problem with this approach was that the population would not necessarily
evolve to this state of highest mean fitness, and he did not take that into
account. A key paper arguing that was:
Gillespie, J. 1973. Polymorphism in random environments.
Theoretical Population Biology 4: 193-195.

It turns out to depend a lot on whether variability is within or between
generations, and other details. What is best for long-term population
survival is not necessarily what evolution will lead to.

--
Joe Felsenstein joe@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Department of Genome Sciences and Department of Biology,
University of Washington, Box 357730, Seattle, WA 98195-7730 USA

.

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