Re: Heritability of fitness

Perplexed in Peoria wrote:
> In the course of preparing my next posting on my "Breadbox" thread,
> I came to the conclusion that there should be a relationship between
> the rate at which information 'about the environment' is accumulated
> in the genome and the heritability of total fitness. Since the
> heritability of fitness strikes me as one of the cornerstones of
> Darwin's theory, I assumed that there must be a host of measurements
> of this important parameter in a variety of wild and laboratory
> populations. So I went to the web to see if I could find them.
>
> What I found instead is that it is generally known and/or believed
> that the heritability of fitness in the wild is too small to measure.
> Some empirical studies report that total fitness heritability was
> undetectable "as expected". Apparently I don't understand evolutionary
> theory as well as I thought I did. The following abstract seems to
> summarize the conventional thinking (and also points out that heritability
> is probably not EXACTLY zero):
>
> Mayo, O., Bürger, R., Leach, C.R.:
> The heritability of fitness: some single gene models.
> Theoret. Appl. Genetics 79, 278-284 (1990).
>
> Summary Because directional selection exhausts additive-genetic variance,
> it is frequently claimed that the heritability of fitness should be very
> close to zero. However, mutation-selection balance generates a certain
> amount of additive-genetic variance, so that even parent-offspring
> measures of heritability may be greater than zero at equilibrium.
> Intra-generation heritability may also be non-zero, providing the
> potentials for genetic change following environmental change.
>
> So my current understanding of this is that the heritability of fitness
> in the wild is near zero at most times and places for most species.
> But occasionally, due to environmental change or the freak appearance
> of a rare beneficial mutation, the heritability of fitness in a population
> rises to a level high enough to actually DO something.
>
> Which leads me to wonder - why was there ANY opposition in the pop gen
> community to Gould's and Lewontin's ideas regarding punctuated
> equilibrium?
>
Did they notice it? Punk eek was Gould and Eldridge, and was
paleontology, not population genetics. The time scales are so
different, it's difficult to link the two.

> Oh, by the way, please ignore my speculations on the "breadbox" thread.
> It appears I am going to have to do some rethinking.
>
> One other comment - I would have thought that there must be enough natural
> environmental change out in the wild, and enough variation capable
> of exploiting that change, that fitness heritability would be large
> enough to measure - at least over timescales in which the new environment
> is constant. But apparently the 'signal-to-noise' ratio is just too high.
>
The problems is that the changes in the environment will lead to changes
in the selective regime, so you might see variation in what fitness
actually is. See this paper, for example:

Merilä, J., L.E. Kruuk & B.C. Sheldon (2001) Cryptic evolution in a wild
bird population Nature 412: 76-79.

Personally, I'm a big fan of the idea that environmental fluctuations
are a major force, ever since my field trials failed one year because of
a lack of rainfall....

Bob

--
Bob O'Hara
Department of Mathematics and Statistics
P.O. Box 68 (Gustaf Hällströmin katu 2b)
FIN-00014 University of Helsinki
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.

Relevant Pages

  • Re: Heritability of fitness
    ... >>in the genome and the heritability of total fitness. ... >>enough to measure - at least over timescales in which the new environment ... > selection with fitness declining away from their optima. ...
    (sci.bio.evolution)
  • Re: Heritability of fitness
    ... >> the rate at which information 'about the environment' is accumulated ... >> in the genome and the heritability of total fitness. ... >> should be very close to zero. ...
    (sci.bio.evolution)
  • Heritability of fitness
    ... in the genome and the heritability of total fitness. ... close to zero. ... due to environmental change or the freak appearance ...
    (sci.bio.evolution)
  • Re: Minimization principal for evolution
    ... every single gene in both species is perfectly adapted to the ... environment they inhabit. ... evolving and none of them have reached the top of any fitness peak. ... This is doubly puzzling since a heritability coefficient for fitness ...
    (sci.bio.evolution)
  • Re: Hard science of evolution
    ... they look at the math carefully and notice the unrealistic ... And show that fitness really is heritable. ... Heritability of fitness seems to be pretty small. ...
    (talk.origins)
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