THE MAINTENANCE OF OBLIGATE SEX IN FINITE, STRUCTURED POPULATIONS SUBJECT TO RECURRENT BENEFICIAL AND DELETERIOUS MUTATION

• Published in: Evolution Vol. 66; no. 12; pp. 3658 - 3669
• Main Authors: Hartfield, Matthew, Otto, Sarah P., Keightley, Peter D.
• Format: Journal Article
• Language: English
• Published: Malden, USA Blackwell Publishing Inc 01.12.2012; Wiley Subscription Services, Inc; Oxford University Press
• Subjects: Alleles; Biological Evolution; Computer Simulation; Evolution; Evolution of sex; Evolutionary genetics; Gene Flow; Genetic loci; Genetic mutation; Hill-Robertson effects; Models, Genetic; Muller's ratchet; multilocus simulations; Mutagenesis; Mutation; Natural populations; Population Density; Population genetics; Population growth; Population migration; Population number; Population size; Population structure; Recombination, Genetic; Selection, Genetic; Sex Characteristics; Sexes; Subpopulations; Two dimensional modeling
• ISSN: 0014-3820; 1558-5646; 1558-5646
• DOI: 10.1111/j.1558-5646.2012.01733.x

Although there is no known general explanation as to why sexual populations resist asexual invasion, previous work has shown that sexuals can outcompete asexuals in structured populations. However, it is currently unknown whether costly sex can be maintained with the weak structure that is commonly observed in nature. We investigate the conditions under which obligate sexuals resist asexual invasion in structured populations subject to recurrent mutation. We determine the level of population structure needed to disfavor asexuals, as calculated using the average F st between all pairs of demes. We show that the critical F st needed to maintain sex decreases as the population size increases, and approaches modest levels as observed in many natural populations. Sex is maintained with lower F st if there are both advantageous and deleterious mutation, if mutation rates are sufficiently high, and if deleterious mutants have intermediate selective strengths, which maximizes the effect of Muller's ratchet. Additionally, the critical F st needed to maintain sex is lower when there are a large number of subpopulations. Lower F st values are needed to maintain sex when demes vary substantially in their pairwise distances (e.g., when arrayed along one dimension), although this effect is often modest, especially if some long-distance dispersal is present.