[continued from previous message]   
      
   >>>> replicate, and the females empty (0N) eggs are used to replicate the   
   >>>> male's DNA.   
   >>>   
   >>> Yes, but how does the queen benefit from this?   
   >>   
   >> The queens DNA benefits because the female likely requires being mated   
   >> before developing into an egg laying machine.  If no male is around no   
   >> eggs get produced.  No M. ibericus progeny.   
   >   
   > So here we see the benefits to us of reading the actual paper, in which   
   > it turns out that all the workers are hybrids. The M. structor male does   
   > indeed contribute to their genomes, which is presumably an advantage in   
   > maintaining genetic diversity.   
      
   Yes, the news article didn't provide what was actually going on.  Hybrid   
   workers seem to be made, but not hybrid queens.  Apparently haploid M.   
   ibericus males are also produced, and they claim that these males are   
   responsible for the diploid queens, but for some reason they didn't find   
   and diploid M. ibericus workers among the larva and eggs that they   
   tested.  It looks like the M. ibericus males are duds and not used for   
   mating.  M. ibericus queens are produced, but are they progeny of the M.   
   ibericus males?  They claimed that their test would identify caste, but   
   they only found hybrid workers.  These colonies have multiple egg laying   
   queens and multiple males in the colony.  I would guess that the colony   
   males would mate with the queens.  So why aren't M. ibericus workers   
   produced?   
      
   They can't seem to get enough DNA from a lot of eggs to do their   
   analysis.  It may be that they have a high frequency of eggs that do not   
   develop.  Insect embryos develop in a weird way compared to vertebrates.   
     By the time they tried to process the eggs for DNA they should have   
   been filled with thousands of nuclei.  They may not be getting the whole   
   story about what is happening.  They know that non disjunction has to   
   happen to form empty eggs that produce the M. structor males, but they   
   don't know what happens to the 2N egg cells that would be expected to be   
   produced or the excess 0N egg cells.  They claim to be finding too many   
   M. structor male containing eggs and larva for the numbers of adults in   
   a colony.  That would mean that they are also finding too many male and   
   queen M. ibericus eggs and larva.  There could be some other winnowing   
   process going on.   
      
   >   
   >>>> 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.   
   >   
   > All moot, given that the workers are all hybrids.   
      
   What kind of hybrids, and why aren't any hybrids queens?  I looked it up   
   and triploid ants can be produced, but they are usually due to diploid   
   sperm fertilizing the eggs.  It produces viable workers, but infertile   
   queens.   
      
   They need to do a ploidy analysis on the workers.   
      
   One paper that google put up on fire ants claimed that four female ants   
   (I assume they meant worker ants, the paper had Japanese authors)   
   produced a range of cell ploidies from the 151 metaphase spreads   
   obtained from them (they had different numbers of chromosomes in their   
   cells).  The female ants cells could be haploid (35.2%), demi-ploidy   
   (1.5N: 16.3%) diploid (38.3%), triploid (2.2%), tetraploid (4.4%), other   
   ploidies (3.6%, some octoploids were found).  So ants can be pretty   
   messed up when they are supposed to be diploid females.  They claim that   
   this gives the fire ants some type of advantage.   
      
   Ron Okimoto   
      
   >   
   >>>> 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.   
   >   
   > Again, moot.   
   >   
      
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