The evolution of the number of sexes

Sexual reproduction is not always synonymous with the existence of two morphologically different sexes; isogamous species produce sex cells of equal size, typically falling into multiple distinct self-incompatible classes, termed mating types. A long-standing open question in evolutionary biology has been what governs the number of these mating types across species, which varies from 2 in many yeasts and algae, to hundreds or even thousands in some multicellular fungi.

In this talk I will describe some recent modelling work that suggests that the rate of sexual reproduction in these species may prove to be a key predictor of the number of sexes observed [1,2,3]. I will then go on to describe my plans for future work investigating the link between mating type number and genetic diversity in these species, with a particular emphasis on the role of sexual reproduction in the evolution of plant pathogenic fungi.

[1] The rate of facultative sex governs the number of expected mating types in isogamous species, Nature Ecology & Evolution, 2018 G.W.A.C, H. Kokko

[2] Invasion and extinction dynamics of mating types under facultative sexual reproduction, Genetics, 2019, P. Czuppon, G.W.A.C

[3] Fitness differences suppress the number of mating types in evolving isogamous species, To Appear: Royal Society Open Science, Y. Krumbeck, G.W.A.C, T. Rogers