Group selection, as I’ve heard it explained before, is the idea that genes spread because their effects are for the good of the species. The whole point of evolution is that genes do well because of what they do for the survival of the gene. The effect isn’t on the group, or on the individual, the species, or any other unit other than the unit that gets copied and inherited.
Group selection is group selection: selection of groups. That means the phenotype is group behavior, and the effect of selection is spread equally among members of the group. If the effect is death, this eliminates an entire group at once—and the nearer a selfish gene approaches fixation, the more likely it is to trigger a group extinction. Consider what would happen if you ran Axelrod’s experiments with group selection implemented, so that groups went extinct if total payoff in the group below some threshold.
The key point is nonlinearity. If the group fitness function is a nonlinear function of the prevalence of a gene, then it dramatically changes fixation and extinction rates.
Well, maybe. If the plant has a typical set of recessive genes in its genome, self-fertilisation is a disaster. A few generations down the line, the self-fertilising plant will have plenty of genetic problems arising from recessive gene problems, and will probably die out. This means that self-fertilisation is bad—a gene for self-fertilisation will only prosper in those cases where it’s not fertilising itself. It will do worse.
No. Self-fertilisation doesn’t prevent cross-fertilisation. The self-fertilizer has just as many offspring from cross-fertilization as the self-sterile plant, but it has in addition clones of itself. Many of these clones may die, but if just one of them survives, it’s still a gain.
Group selection is group selection: selection of groups. That means the phenotype is group behavior, and the effect of selection is spread equally among members of the group. If the effect is death, this eliminates an entire group at once—and the nearer a selfish gene approaches fixation, the more likely it is to trigger a group extinction. Consider what would happen if you ran Axelrod’s experiments with group selection implemented, so that groups went extinct if total payoff in the group below some threshold.
The key point is nonlinearity. If the group fitness function is a nonlinear function of the prevalence of a gene, then it dramatically changes fixation and extinction rates.
No. Self-fertilisation doesn’t prevent cross-fertilisation. The self-fertilizer has just as many offspring from cross-fertilization as the self-sterile plant, but it has in addition clones of itself. Many of these clones may die, but if just one of them survives, it’s still a gain.
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