Evolution of reproductive systems in filamentous ascomycetes. Ii. evolution ofhermaphroditism and other reproductive strategies

Abstract

The evolution of different reproductive systems in filamentous ascomycetes is studied in a population genetic model. These fungi differ essentially from higher plants and animals because mating types can exist in addition to male and female gametes, and the conidia serve as both male gametesand asexual spores; moreover, selfing is genetically equivalent to asexual reproduction in thesehaploid organisms. A variable fitness of ascospore production is predicted as the explanation for theevolution of two systems that abundantly exist in nature: hermaphroditism in heterothallic speciesand the formation of both asexual and sexual spores in homothallic species. Imperfect fungi willevolve if sexual spores do not show a remarkably higher fitness than asexual spores. © 1992 The Genetical Society of Great Britain.