[ExI] IQ and beauty

[rex]

John Clark <johnkclark at gmail.com> [2015-10-08 20:58]:
>    On Thu, Oct 8, 2015 at 10:29 PM, rex <[1]rex at nosyntax.net> wrote:
> 
>      ​> ​There are many examples of semi-cyclic population levels, but
>      extinctions?
> 
>    ​There are vastly more examples of extinctions than there are of
>    ​semi-cyclic population levels

Sure. You omitted the context, but Dan sussed what I meant:

 "I believe this and the earlier parts of his post were asking you
  about linking actual extinctions to the mechanism -- not merely
  saying there are plenty of extinctions.

Current thought is that the large majority of species that have ever
existed are extinct, but that's irrelevant to my observation that a
"just so" argument that exaggerated traits may progress to extinction
does not imply that they will frequently do so.  It's similar to
group selection: it seems plausible and was accepted without question
for decades. Eventually, the conditions necessary for group selection
were elucidated and found to be be so restrictive that group selection
almost never happens in the wild. 

I suspect extinctions due to runaway exaggerated traits are also
rare. So far, not a single example has been presented. A quick search
didn't turn up any examples, but it did reveal an example where sexual
dimorphism "improved the carrying capacity of the environment, and thus
presumably population viability."

http://www.kokkonuts.org/wp-content/uploads/Sexy2die4.pdf

[Full text at above URL]


Ann. Zool. Fennici
40: 207–219 ISSN 0003-455X
Helsinki 30 April 2003 © Finnish Zoological and Botanical Publishing Board 2003

Sexy to die for? Sexual selection and the risk of extinction

Hanna Kokko & Robert Brooks

Sexual selection is a field with a strong focus on the "costs " of
traits. However, whether such costs have an influence on the
demography of the population is very rarely discussed. Here we present
various processes through which sexual selection might have an impact
on population viability and thus increase or decrease the risk of
extinction.

We argue that evolutionary ‘suicideʼ — as sometimes suggested e.g. to
have caused the extinction of the Irish elk — is unlikely in
deterministic environments, except if costs are not paid by the same
individual that bears the trait. Thus, intra- or inter-locus sexual
conflict could in principle drive a population extinct, and we do not
know why this does not frequently happen. Whether sexual selection
increases or decreases extinction risks when populations face variable
or unforeseen environmental conditions is likewise unknown, and we
outline mechanisms that could account for either pattern.  Inbreeding
is another factor that could either increase or decrease population
viability in sexually selected species. Inbreeding may be caused by a
high mating skew, but it could also be reduced if females adaptively
choose mates to avoid inbred offspring.  Finally, when intraspecific
competition for resources is taken into account, it is unclear how
individual viabilities translate to extinction risks faced by the
population. We show an example where greater mortality of males due to
sexual dimorphism improves the carrying capacity of the environment,
and thus presumably population viability.


http://humancond.org/_media/papers/crespi04_vicious_circles.pdf

http://www.bio.uib.no/evofish/papers/BoukalBerec2002_JTB.pdf

-rex
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