Validity of the theory of sex in relation to parasites.

Xia xia at darwin.genetics.washington.edu
Sun Dec 6 18:26:15 EST 1992

In article <Byt9vv.Jw8 at usenet.ucs.indiana.edu> adpeters at sunflower.bio.indiana.edu (Andy Peters) writes:
>In article <1992Dec5.195711.22967 at u.washington.edu> xia at darwin.genetics.washington.edu (Xia) writes:

>>No, it does not make sense, because it applies only to specialised
>>host-parasite pairs. When the host is harbouring many different species
>>of parasites, a recombination to avoid one species of parasite would 
>>send the host to the mercy of other species of paes.
>I disagree.  No matter how many parasites are coevolving with the
>host, each parasite population will be tracking the most common
>host genotype.  By "tracking," I mean that the parasite populations
>will constantly be evolving to mimic some feature of the host (not
>necessarily the same feature for each parasite).  Hence, recombining
>and producing rare offspring allows the host a chance to escape from
>any number of parasites.
>> Also, the
>>theory would require sex to evolve independently many times. 
>I'm not sure why this is correct anyways, but it's not relevant
>because the Red Queen applies to the _maintenance_, not the _origin_
>of sex.
>>the theory requires the diversified recombinants to be realized in
>>progeny. For this reason it does not apply to species with low fecundity.
>This is true of some other ecological-genetic hypotheses for the
>maintenance of sex (i.e. the tangled bank), but I don't think it's
>true for the Red Queen.  The Red Queen model states that the
>production of _rare_ progeny, not _diverse_ progeny, is the benefit of
>sex.  Granted, the production of large numbers of progeny will help
>ensure that some of them are rare, but so will increased recombination
>* Andy Peters                     * I borrowed Dad's jack.  I'll *
>* Program in Evolution,           *   return it and his rivet    * (<-Don't
>*      Ecology, and Behavior      *        gun tomorrow          *     ask)
>* Indiana University, Bloomington *            -Bob              *

Are there many people agreeing with Andy? If there are, then I will
post responses, otherwise I will communicate with Andy only.

Xuhua Xia
Department of Genetics
U of Washington

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