[continued from previous message]   
      
   started with enough genetic variation to keep producing highly   
   polymorphic populations.   
      
   >   
   >> What is lost is the ability to gain new genetic variants due to normal   
   >> sexual reproduction.  In this case the queen posesses a highly   
   >> polymorphic genome that has been repeatedly tested and won out to   
   >> create an expanding population with the same starting genetics.   
   >   
   > Again, do you actually know that the genome is highly polymorphic,   
   > whatever that means in an effective population size of one?\   
      
   The authors claim that the parthenogenetic species is highly   
   polymorphic, but my guess is that it may not be as polymorphic as the   
   sexually reproducing outcrossing species.  The parthenogenetic colonies   
   may be as polymorphic as any individual normal M. ibericus colony.  It   
   sounds like M. ibericus relies on inbreeding in that male and female   
   sibs create the new colonies.  I would expect the normal amount of   
   genetic variation in an M. ibericus colony to be low, and they normally   
   rely on the most polymorphic sib pairing to produce successful colonies.   
     the normal M. ibericus may also reproduce selfishly and not want to   
   reproduce someone else's DNA, but the species has to pay the price for   
   doing inbreeding within a family.  Non disjunction is better than sib   
   matings for keeping the DNA within the family.   
      
   >   
   >> Each new queen would have a different combination of genetic variation   
   >> inherited from the original queen.  Any combination that isn't as   
   >> successful would be out competed.   
   >   
   > I just can't see recombination of this sort as producing much selectable   
   > variation.   
   >   
      
   Position effect is when a genes position on the chromosome is associated   
   with how well it functions.  When you change the linkage you change what   
   alleles of flanking genes exist to affect the expression of alleles   
   nearby.  Just think about recombination around a deleterious loci.  One   
   of the models for heterosis is linkage to deleterious loci.  The loci   
   flanking a deleterious loci may have selective advantage, but   
   heterozygousity (hybrid vigor) is maintained because homozygotes are   
   selected against.  Recombination shuffles the variants around the   
   deleterious loci.  Gene interaction is likely very important (everything   
   has to work with everything else that is working) and it has long been   
   posited that the arrangement of alleles along the chromosome was   
   important (often genes involved in the same biochemical pathway or   
   function in the organism are found in close linkage on the same   
   chromosome).  Closely linked loci are more likely to be inherited   
   together, so if you create a linkage between two variant alleles that   
   have some selective advantage together the progeny are more likely to   
   inherit both of those alleles.  If recombination still occurs in these   
   queens they can produce many offspring with new linkage arrangements.   
   New advantageous linkage arrangements are more likely be be inherited   
   together.  They can change the linkage with a deleterious allele so that   
   the advantageous flanking alleles can be fixed in the population and the   
   deleterious allele can eventually be lost.   
   Ron Okimoto   
      
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