Re: Cost of sex - a bargain!


John Harshman wrote:
allanm wrote:

Windy wrote:

allanm wrote:

My contention here is that meiotic defection, all other things being
equal, is selectively neutral. The two-for-one cost cannot be realised
because, as far as I can see, the defector cannot arise in such a way
that males are disfavoured with respect to the defector locus.

There are two 'alleles' - homologues, really, because there is
reproductive isolation: - Be-Asexual and Don't-Be-Asexual.
Don't-Be-Asexual is copied into every male and female descendant of a
sexual population. If not, where does it reside, in the genome?

Be-Asexual will get copied into each and every descendant.
Don't-Be-Asexual can only be sure of getting into 50% of the
descendants; in others, it may be supplanted by Don't-Be-Asexual-2,
Don't-Be-Asexual-3, or any other allele; even Be-Asexual, in case the
asexuality only manifests in some conditions.

-- w.


You really are missing it; I'm sorry to sound contentious. It doesn't
matter what gene Be-Asexual arose from.

Don't-Be-Asexual is not an 'allele' of Be-Asexual at all.
Don't-Be-Asexual is the ancestral state - all alleles, anywhere, which
do NOT promote asexual reproduction. in a functional sexual female.
"It" - a disparate set of genes - is copied to EVERY offspring of a
sexually reproducing female. There is no 50% gain for a ***defecting***
gene.

No. What there is is a 50% gain for all alleles present in any genome
that has the Be-Asexual allele. Therefore all those alleles will
increase in frequency. You could if you like consider them all as
hitchhikers except for Be-Asexual.

I do consider them as hitchhikers. More importantly, they have all
hitched the same ride. The gaining of copies by selective processes in
a sexual genome is not the same thing as the incidental gaining of
nonselected copies, whatever the ratio. Particularly when the mode of
assortment, and units of gene selection, from that moment on, are
completely changed from the sexual type. The whole genome of an asexual
is selected as a piece. An allele in a sexual is 'tested' by selection
as it works in conjunction and competition with many other different
alleles, separately and together, at its own locus and at others.

There is a case for saying that this is a speciation event, even if
Be-Asexual is a recessive member of the sexual genome. It can only
increase by drift, and is not phenotypically expressed in the sexual.
Every time it meets itself, it pops it and every allele in that genome
into a very different mode of operation. The sexual genome is
completely unaffected by this event - unless, in the fullness of time,
it has to deal with these individuals as competitors for food, space
etc. It is likely to be well equipped to do so, as varied sexual
genomes tend to be.

This is not a killer mechanism for females to subvert males.


Males have daughters too; has everyone forgotten that? Where do their
genes come from?

Half from the father, half from the mother. So the mother's genes could
be reproduced twice as much by dispensing with the father. What does the
fact that males have daughters contribute to this?

Sexual females produce gametes. Not male or female gametes. Males
produce gametes which, for the vast majority of their DNA, are
essentially the same as female. The machinery for female sexual
reproduction is represented fully in all those gametes.

Any *individual* maternal allele can be doubled by going asexual, yes
(but see above - NOT the one which defects). But she does not halve her
output of "sexually reproducing female" genes by liaising with, or
producing, males. In fact, inasmuch as males exploit females, male
offspring are an effective means of females getting in on that act also.

.

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