Re: Sergey Gavrilets and the adaptive landscape

dkomo <dkomo871@xxxxxxxxxxx> wrote in
news:dkb125$107d$1@xxxxxxxxxxxxxxxxxxx:

> Wirt Atmar wrote:
>
>
>>
>> The nearly complete decoupling between the range of mutations
>> expressed and the shape of the adaptive topography intrinsically
>> makes evolutionary optimatization algorithms surprisingly resistant
>> to entrapment in local optima. Perhaps completely counter-intuitive,
>> it is not the height of the intervening barrier that represents the
>> problem to continuing evolution but its width.
>>
>> With this introduction, to continue the discussion, please see:
>>
>> http://aics-research.com/research/notes.html#IID
>>
>> Wirt Atmar

>
> As far as I can tell, everything you wrote here and on the above web
> page assumes a static fitness topology. Is that right? Yet, in the
> real world the environment is constantly changing, which will affect
> the topology of the fitness landscape. This can also happen if a
> population of animals migrates to a new location or encounters a new
> type of predator or prey. So a particular population can rather
> quickly shift from being on the slopes of a local peak to being at the
> bottom of a valley due to these kind of environmental changes.
>
> I don't see how a static fitness landscape can realistically model
> biological evolution. You must take into account that the landscape
> is itself dynamic.
>

There is an interesting article that discusses this in the 9/25/2005
Science, p. 2075 "Phenotypic Diversity, Population Growth, and
Information in Fluctuating Environments" by Kussell and Leibler. I have
not yet read the article itself, but the Perspective piece (p. 2005) on
it makes several points: that the reproductive success in fluctuating
environments can be calculated using the Lyapunov exponent (whatever that
is). That in a fluctuating environment organisms respond by randomizing
their phenotype, known as bet-hedging. That selection may favor
"stochastic switching" - producing variable offspring by chance - over
"responsive switching" - producing variable offspring only after sensing
a change in the environment. This last would support Larry Moran's
contention that organisms are often not well adapted - but it might be
considered an "adaptationist" explanation for observed stochasticism :-)

Yours,

Bill Morse

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