PT - JOURNAL ARTICLE
AU - Novak, Sebastian
AU - Barton, Nicholas H.
TI - When Does Frequency-Independent Selection Maintain Genetic Variation?
AID - 10.1534/genetics.117.300129
DP - 2017 Oct 01
TA - Genetics
PG - 653--668
VI - 207
IP - 2
4099 - http://www.genetics.org/content/207/2/653.short
4100 - http://www.genetics.org/content/207/2/653.full
SO - Genetics2017 Oct 01; 207
AB - Frequency-independent selection is generally considered as a force that acts to reduce the genetic variation in evolving populations, yet rigorous arguments for this idea are scarce. When selection fluctuates in time, it is unclear whether frequency-independent selection may maintain genetic polymorphism without invoking additional mechanisms. We show that constant frequency-independent selection with arbitrary epistasis on a well-mixed haploid population eliminates genetic variation if we assume linkage equilibrium between alleles. To this end, we introduce the notion of frequency-independent selection at the level of alleles, which is sufficient to prove our claim and contains the notion of frequency-independent selection on haploids. When selection and recombination are weak but of the same order, there may be strong linkage disequilibrium; numerical calculations show that stable equilibria are highly unlikely. Using the example of a diallelic two-locus model, we then demonstrate that frequency-independent selection that fluctuates in time can maintain stable polymorphism if linkage disequilibrium changes its sign periodically. We put our findings in the context of results from the existing literature and point out those scenarios in which the possible role of frequency-independent selection in maintaining genetic variation remains unclear.