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Sexual Selection

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Sexual Selection

Postby ilmc90 » Mon Nov 08, 2010 1:02 am

I have a specific question regarding sexual selection and female preference. The follow is a quote from an evolution text book:

In the tungara frog, the male call consists of the basic “whine” that is found throughout this group of species, but also has additional “chucks”. (The female) strongly prefer calls with extra chucks. This preference arises because the chuck frequencies are tuned to stimulate the basilar papilla, one of two sound-sensing organs in the frog’s inner ear. Crucial evidence that the “chuck” evolved to exploit a preexisting sensory bias comes from the observation that in related species males do not have the distinctive “chuck”, yet females have a strong preference for recorded calls containing this chuck. Other things being equal, this male trait would increase if it arose in those species. Examination of the distribution of trait and preferences across the phylogeny shows that the preference evolved before the trait. Selection on the preference therefore cannot have anything to do with the trait that happens to be preferred, because the preference was present before the trait evolved.

Although the female preference for the "chuck" is genetic, males use it to their advantage to attract females. Thus, males who have this trait are more likely to reproduce. Is my interpretation correct? Can someone explain this to me?
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Re: Sexual Selection

Postby enarees » Mon Nov 08, 2010 5:58 am

Remember "autosexual extraction"!
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Postby canalon » Mon Nov 08, 2010 2:19 pm

Correct interpretation on your part.
"Chuck" sensitivity was pre-existent (you can see it in related species), but mostly unused by males. When the by accident a male that could generate those was born, he was much more likely to mate than the others. And if the trait was inherited, so was his male offspring. And everytime the number of chucks increased, the more likely they were to mate and multiply. So quick fixation of an advantageous trait.

and a massively good advice: Ignore enarees
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Science has proof without any certainty. Creationists have certainty without
any proof. (Ashley Montague)
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Re: Sexual Selection

Postby BDDVM » Sat Nov 13, 2010 4:05 am

Your confusion over these frogs carnal activities is understandable. They don't fit with some current interpretations of sexual selection. Fitness indicators/ handicap theory don't have anything to say about these frogs.
Handicap theory states that females benifit by selecting males that display in such a way as to prove their overall fitness. This leads to displays thay are increasingly costly. Peacocks tails.
My biggest problem with this theory is it doesn't give any reason for removing males who have great genes and no costly display.
Then there's the problem of trying to explain away costly (bad) displays by saying that they are so bad they must be good.
Without some kind of cognitive bias male peacocks would not have to drag that idiotic tail around.
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Re: Sexual Selection

Postby enarees » Mon Nov 15, 2010 7:22 am

BDDVM wrote:...
Without some kind of cognitive bias male peacocks would not have to drag that idiotic tail around.


Things are simple:
Some females have liked parthenogenate rooster with long tail.
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Re: Sexual Selection

Postby Rap » Wed Jan 19, 2011 5:28 am

Any ideas on what makes the females responsive to the chucks in the first place? I mean, I have heard the theory that some eye disease among proto-peacocks which correlated with lack of fitness encouraged the tendency of the females to select males with "healthy eyes", which in turn encouraged the tendency of males to display "healthy eyes", and the fact that the females were being "fooled" by eyes on the tails was rendered less important after the disease disappeared. The sexual selection feedback loop was established, and the negative aspects of the elaborate displays were not sufficient to extinguish the trait quickly. Any ideas on the chuck scenario? How was this preference established in the first place, and why was the male response extinguished in some cases but not others?
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Re: Sexual Selection

Postby ruiseixas » Tue May 24, 2011 10:46 pm

Before thinking about how dimorphism evolves, it's much more important to think in why exists in the fist place.
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