[continued from previous message]   
      
   most heterozygous females were selected by how well their colonies did.   
   Highly heterozygous females would produce highly polymorphic non   
   disjunction offspring.  This is essentially an instant speciation from   
   M. ibericus.  Each new colony is essentially a new lineage (species) no   
   longer interbreeding with the others, but they maintain a high degree of   
   the M. ibericus genetic variation likely due to selection for   
   heterozygousity in the queens.   
      
   >   
   >>>> The ant male DNA also benefits from this arrangement.  Clonal   
   >>>> offspring are produce that keep perpetuating the male's DNA each   
   >>>> generation.  It is pretty much a win win for the selfish DNA.  The   
   >>>> DNA of two divergent species is preserved in one population, and   
   >>>> they are preserved as intact genomes.   
   >>>   
   >>> Again, what benefit does the female genome derive from this process?   
   >>> Why wouldn't evolution dispense with the male, unless it has some   
   >>> essential function that's hard to get rid of?   
   >>   
   >> The selfish DNA proposal would have this situation selected for   
   >> because it transfers the individual's DNA without having to mix with   
   >> other DNA.   
   >   
   > The queen's DNA shouldn't care what happens to the male's DNA. And the   
   > male's DNA has no power to influence its own reproduction. So we still   
   > have to ask why the queen would bother mating at all.   
      
   You can think of each being selfish parasites on the other.  The queen   
   doesn't need the males DNA, but the male doesn't care because it can use   
   the empty eggs that the queen has to produce in order to reproduce   
   herself, and the queen needs to allow the parasitism because she needs   
   to mate with a male.  They prey on each other to reproduce themselves.   
      
   >   
   >> Both the male's and the queen's DNA get transferred intact to the next   
   >> generation, and the queen is able to do this in a way that maintains   
   >> high genetic variation among her offspring without having to share the   
   >> success with someone else.   
   >   
   > Yet this ability does not depend on preserving the male's genome or upon   
   > mating with a male.   
      
   But the way that the queen reproduces herself requires a male, and also   
   produces empty eggs that the male can use to reproduce itself.  The   
   species does need the male DNA to produce males for the next generation,   
   but that DNA is not used in the normal way by the queen to reproduce her   
   DNA.   
      
   >   
   >>>>> I had assumed that females result from fertilized eggs, each with a   
   >>>>> full, haploid M. structor genome and a haploid M. ibericus genome.   
   >>>>> Of course the problem with that is how you would get genetic   
   >>>>> divergence between the species, given recombination during meiosis.   
   >>>>   
   >>>> You might get recombination if the chromosomes match up, but after   
   >>>> repeated generations using the cloned male genome the species would   
   >>>> eventually become inbred M. structor, so there would be a species   
   >>>> switch eventually.  The first generation you get 50% M. structor   
   >>>> DNA. The next generation you become 75% M. structor DNA.  The next   
   >>>> generation you get 87.5% M. Structor offspring etc..  So when they   
   >>>> claimed that the genomes remained highly polymorphic and M. ibericus   
   >>>> I assumed that any hybrids had to be dead.   
   >>>>   
   >>>>>   
   >>>>>> It could be a case of Dawkin's selfish DNA.  The DNA of the queen   
   >>>>>> devised a means of perpetuating its genetics in a way that   
   >>>>>> prevented inbreeding depression, while being able to generate new   
   >>>>>> segregating genetic diversity among the daughter queens if the   
   >>>>>> ants still have genetic recombination before Meiosis I.   
   >>>>>   
   >>>>> How can you get or retain much diversity? Wouldn't that result in   
   >>>>> complete homozygosity after only a few generations? The male is   
   >>>>> contributing nothing.   
   >>>>>   
   >>>> If the nondisjuction event occurs in meiosis I, meiosis II results   
   >>>> in chromatid splitting in a full diploid genome.  I called this a   
   >>>> tetraploid egg because that is what the composition of the egg cell   
   >>>> would be if you started with a tetraploid and had a normal Meiosis I   
   >>>> separation of homologous chromosomes.   
   >>>>   
   >>>> Since recombination occurs before Meiosis I you maintain genetic   
   >>>> diversity and do not just produce clones.  When the chromatids split   
   >>>> at Meiosis II, recombined genetically unique chromosomes can go into   
   >>>> each egg cell.   
   >>>>   
   >>>> I used to make my genetic students understand Meiosis.  I would tell   
   >>>> them that if they understood meiosis that they would understand   
   >>>> Mendelian genetics.   
   >>>   
   >>> Nevertheless, you start with a single diploid individual, and that's   
   >>> limited genetic diversity. Recombination within a single genome can   
   >>> only introduce a little, and mutation a little. Keeping in mind that   
   >>> the effective population size (queens only) is likely to be small,   
   >>> how is any significant diversity maintained?   
   >>>   
   >> Mutation rate is essentially the same because both copies of the   
   >> genome of the 2N species is mutated every generation, and only half is   
   >> transferred to the next generation.  In this case the 2N is   
   >> transferred to the next generation, so it is the same as having   
   >> another half mutated genome incorporated instead.  The queen is highly   
   >> heterozygous and is segregating a lot of genetic variation, but this   
   >> variation is not segregating normally.   
   >   
   > Is the queen in fact highly heterozygous? What maintains heterozygosity?   
   > Does recombination, in most cases, even produce selectable variation?   
   > Most of the genome is junk, and the bits that aren't mostly don't care   
   > which chromatid they're on or which nearby variants are on. I can see   
   > crossover within an exon possibly producing a new, functionally   
   > different allele, but how often would even that happen?   
      
   Selection.  If recombination doesn't occur normally then all the queens   
   would be highly heterozygous clones.  If recombination does occur then   
   the queen doesn't produce clones, but new chromosomal haplotype   
   combinations each generation, and it sounds like the most heterozygous   
   queens get selected because they produce the most successful highly   
   polymorphic colonies.   
      
   >   
   >> Instead of transferring half of the variation to the next generation,   
   >> she is transferring it all, but there are a near infinite number   
   >> variant packages that she can transfer when you consider genetic   
   >> recombination and new mutation.  Every meiosis she generates a whole   
   >> new set of chromosomal haplotypes to pass on to her offspring.   
   >   
   > Yes, but how many of them have any functional differences. The genome is   
   > transferred with all the same bases, just swapped to different   
   > chromatids now and then. Heterozygosity increases only through mutation.   
      
   Probably a lot of the different combinations have functional   
   differences, and the new combinations around the chromosomal break   
   points would persist with decreasing size for many generations.  The   
   drawback to this is as you and I previously pointed out you lose the   
   abilty to acquire more genetic variation by outcrossing, but a selfish   
   DNA success doesn't look that far into the future.  Parthenogenetic   
   species like this might be doomed to extinction unless they can produce   
   enough new colonies to keep selecting the most fit for their current   
   environment.  This is true for all parthenogenetic species that produce   
   basically clonally.  Those that do reproduce clonally have to rely on   
   new mutation to save them under changing selection pressure.  This case   
      
   [continued in next message]   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)