Re: A simple model exhibiting Haldane's limit

"Perplexed in Peoria" <jimmenegay@xxxxxxxxxxxxx> wrote in
news:e8ct4g$1naq$1@xxxxxxxxxxxxxxxxxxx:

(Snip)

Now this raises the question of whether the Haldane limit is a
biological phenomenon or a modeling phenomenon. Our model truncates a
nominal fitness of 2.5 to 2 because there doesn't seem to be any other
possible response within the structure and assumptions of the model.
But how might Nature respond to this problem (or rather, opportunity)?
Well, one thing that a particularly fit slime cell might do is to
reproduce more rapidly than its peers (thus violating our modeling
assumption of a fixed and non-overlapping generation time). But that
might get it into trouble if there is some kind of synchronization of
mating behavior. The early slime fails to find a mate. Or, another
thing it could do is to insert a round of mitotic division into the
period during which it is waiting for everyone else to be ready for
sex. A biological or a modeling phenomenon? I guess I don't know.
It could be either. The thing is, we are not going to be able to
conduct real-world experiments to resolve this question. My graph of
rate of substitution vs rate of mutation can only be drawn by an
experimenter investigating models. There is no good way to vary the
rate of advantageous mutation in a biological experiment.

Some quibbles on a well thought-out post:

The thing that bothers me about the above supposition is that it seems to
me that more "fit" (by which I mean more specially adapted to their
environment) species tend as a rule to be K selected rather than r
selected. If I am right in this, then either we have to admit group
selection or more fit individuals do not respond by reproducing more
rapidly.

A second point is that in fact non-sexual reproduction does occur
seasonally among aphids. Someone - I apologize for not remembering who -
pointed this out to me in a fairly recent thread. This may correspond to
your second alternative for increasing the fitness of an individual that
is otherwise constrained to a fixed generation time - in the case of
aphids and many other temperate zone plants and animals due to seasonal
weather patterns.


Yours,

Bill Morse

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