Invasion and Extinction Dynamics of Mating Types Under Facultative Sexual Reproduction

• Published in: Genetics (Austin) Vol. 213; no. 2; pp. 567 - 580
• Main Authors: Czuppon, Peter, Constable, George W A
• Format: Journal Article
• Language: English
• Published: United States Genetics Society of America 01.10.2019; Oxford University Press
• Subjects: Alleles; Animals; Biological Evolution; Cell Communication - genetics; Endangered & extinct species; Evolution; Extinction; Gametes; Genetics; Genetics, Population; Germ Cells - growth & development; Hypotheses; Investigations; Life Sciences; Mating; Mating types; Models, Biological; Mutation; Natural populations; Polymorphism; Population; Population genetics; Populations and Evolution; Probability distribution; Reproduction; Reproduction (biology); Reproduction - genetics; Reproductive system; Sexual Behavior, Animal; Sexual reproduction; United States > US; facultative sex; isogamy; frequency-dependent selection; mating types; self-incompatibility; finite populations; balancing selection; Facultative sex; Mating types; Finite populations; Balancing selection; Frequency-dependent selection; Isogamy; Self-incompatibility
• ISSN: 1943-2631; 0016-6731; 1943-2631
• DOI: 10.1534/genetics.119.302306

In sexually reproducing isogamous species, syngamy between gametes is generally not indiscriminate, but rather restricted to occurring between complementary self-incompatible mating types. A longstanding question regards the evolutionary pressures that control the number of mating types observed in natural populations, which ranges from two to many thousands. Here, we describe a population genetic null model of this reproductive system, and derive expressions for the stationary probability distribution of the number of mating types, the establishment probability of a newly arising mating type, and the mean time to extinction of a resident type. Our results yield that the average rate of sexual reproduction in a population correlates positively with the expected number of mating types observed. We further show that the low number of mating types predicted in the rare-sex regime is primarily driven by low invasion probabilities of new mating type alleles, with established resident alleles being very stable over long evolutionary periods. Moreover, our model naturally exhibits varying selection strength dependent on the number of resident mating types. This results in higher extinction and lower invasion rates for an increasing number of residents.