Re: Article: No sex for 40 million years? No problem

In your recent parthenogenesis scenario the alleles would scarcely be
divergent.
The rate of mutation would be independent of the mode of
reproduction. The alleles would mutate just as fast if the creatures
were sexually reproducing or if they were already parthenogenic. If
the creatures were inbred, Mendelian segregation would ensure that
each line would have a good percentage of the mutated alleles.
Binominal statistics would ensure that some of the lineages would have
more mutated alleles than others.
The geneticist you site seems to assume that the rotifers were
parthenogenic all the way back to their common ancestor. He is
assumming that parthenogenesis evolved just once and only once in the
b. rotifers. Then, the variation that ones sees would have to
accumulate in each lineage separately. A large variation would then
imply that there was no sex for a long time.
In my proposed scenario, parthenogenesis arose independently in
most of the lineages due to the selection pressure caused by
inbreeding barriers. Of course, some mutations would make the
individual more fit by simply removing the inbreeding barrier. Than
the organism could mate with other rotifers and reproduce to its
hearts content. In a parasite-ladden environment, this would be the
safest strategy. However, some mutations would make the individual
more fit by allowing the organism to reproduce parthenogenically. In a
harsh environment with few parasites, this would be the safest
strategy. My gues is that these rotifers live in the latter.
This scenario is based on an imperfect understanding of
Mendelian segregation. I don't have a modern text on Mendelian
segregation. A more recent citation would be better, but I will cite
my sources anyway. I got my description of Mendelian segregation from
a 1916 text:
Edward M. East and Donald F. Jones, "Inbreeding and
Outbreeding" (Lippencott, 1917).



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Relevant Pages

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