Validity of the theory of sex in relation to parasites.

Andy Peters adpeters at sunflower.bio.indiana.edu
Wed Dec 9 19:28:26 EST 1992

In article <1992Dec9.202343.7416 at frc.maf.govt.nz> jbj at frc.maf.govt.nz (Brian Jones) writes:
>Most parasites I know of rely on sex just as much as the host. However they
>have two problems. 1) to find a host animal to infect 2) once in/on the host,
>to establish themselves.
>For 1) sex seems to be almost essential in providing the diversity necessary
>to cope with minute changes in the host genotype, but more frequently changes 
>in the environment. 

The discussion of asex in parasites is tangential to the discussion of
the Red Queen.  In addition, I would argue that since, in most cases,
there are several parasite generations per host generation, parasites
have (relatively) plenty of time to adjust to changes in the host.  It
is interesting (though not conclusive) that those parasites which are
strictly asexual - viruses, bacteria (conjugation not included),
trypanosomes - have _many_ generations per host generation.

I'm not sure I've gotten a good handle on your opinion of the Red
Queen here.  Do you agree that recombination is a good way to reduce
the risk of parasitized offspring?

>Once a parasite has found a host, rapid duplication of the successful
>genetic material is accomplished by asexual means.

* 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              *

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