3
$\begingroup$

For example, Refardt, Bergmiller & Kummerli (Proceedings Royal Society-B, 2013; http://rspb.royalsocietypublishing.org/content/royprsb/280/1759/20123035.full.pdf) model bacteria that have been infected and that commit suicide in order to prevent the spreading infection to the rest of the population. They do so even though relatedness is low, approaching zero.

Two questions:

  • In section 3c, they write

    (A)ltruistic host suicide cannot evolve with $r=0$ because populations go extinct before invasion of the Abi trait is possible. Thus, we predict marginal relatedness ($r < 0$) to be required for successful invasion.

    I am assuming this is a typo and they mean $r>0$?

  • In a situation in which altruism is not directed toward any particular individual(s) but is rather allocated to the whole population, doesn't $r$ depend upon the frequency of the allele that is engaging in the altruism? If it is a new mutation and there is no other allele in the population to receive the benefit, then r=0. If the allele has gained fixation, $r=1$ and selection is much more likely to favor the altruism.

What is a way of modeling whether selection will favor fixation of a new mutation that allocates benefits to the population but not any particular individual (e.g., by committing suicide), given that the new mutation is not shared by (m)any other individuals and consequently, $r$ is initially very low? I would think there is a way of determining the odds that genetic drift would lead the new mutation to develop a substantial enough frequency to increase the odds that the resources would benefit holders of the allele. But I am unfamiliar.

$\endgroup$
1
$\begingroup$

I have not read the paper but here is my guess and a hint

Is it a typo?

Yes, I think so

In a situation in which altruism is not directed toward any particular individual(s) but is rather allocated to the whole population, doesn't r depend upon the frequency of the allele that is engaging in the altruism?

Yes

f it is a new mutation and there is no other allele in the population to receive the benefit, then r=0. If the allele has gained fixation, r=1 and selection is much more likely to favor the altruism.

If the allele that is causing altruism has reached fixation, then there is no more selection as there is no genetic variance in the population.

$\endgroup$
  • $\begingroup$ "If the allele that is causing altruism has reached fixation, then there is no more selection as there is no genetic variance in the population." You're right. I apologize. That was a mistake. But the question still stands: If it's a new mutation, r=0. If the allele has substantial frequency, r is closer to 1, and it is more likely to be selected. The ways of modeling drift and selection that I have seen involve stable fitness. Is there a way of modeling the effects of drift and selection when fitness is frequency dependent? $\endgroup$ – sterid Mar 21 '17 at 20:19

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.