[continued from previous message]   
      
   before developing into an egg laying machine.  If no male is around no   
   eggs get produced.  No M. ibericus progeny.   
      
   >   
   >> My guess that initially the hybridization between the two species   
   >> selected for queens prone to non disjunction in Meiosis I.  These   
   >> defective queens would have been the ones to benefit from mating with   
   >> another species whose DNA they didn't need.   
   >   
   > What benefit?   
      
   Below.  A female prone to nondisjunction is at a disadvantage because   
   she is producing empty eggs (0N) and 2N egg cells, so she will produce   
   too many 1N male offspring, and not enough 2N workers and most of the   
   workers that she does produce may have issues as triploids (they may be   
   inviable).  Mating with a different species allowed the female to switch   
   her egg fertilization strategy.  Normally she would produce just enough   
   unfertilized eggs to produce males, but now she doesn't want the male to   
   fertilize the eggs.  Her strategy had to switch to preventing male   
   fertilization.  Initially the hybrid 2N hybrid progeny (they would have   
   been produced until a high frequency of non disjunction was attained)   
   were likely infertile queens, so the non disjuction females would have   
   been selected for reproduction.  This probably allowed selection for   
   increased frequency of non disjuction and an increse in producing   
   unfertilized eggs.   
      
   >   
   >> For normal matings the triploids produced would have difficulty   
   >> reproducing or there might have been a lot of dead triploid embryos   
   >> produced, so the queens prone to non disjunction would have been   
   >> selected against.   
   >   
   > The question isn't why the queens mate with non-conspecifics. The   
   > question is why they mate at all.   
   The females likely need to mate before completing their development into   
   egg laying machines, and there is also the selective factors of evolving   
   an animal prone to a high frequency of non disjunction.  Mating with   
   another species where the hybrid had reproductive issues would select   
   for the unfertilized non disjunction queens.  This would allow for   
   selection for non disjunction and shifting to producing more   
   unfertilized eggs.   
      
   Ron Okimoto   
      
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