The role of sex in fungal evolution.

Sex in fungi is often associated with dispersal and dormancy, but in many species is not required for reproduction, and its evolutionary genetic role is unclear. Sex can accelerate adaptation to a new environment, and recombination in Saccharomyces cerevisiae, though historically rare, has had a prominent role in the origins of many sequenced strains, in particular the origin of clinical strains from domesticated ancestors. Sex and recombination have recently been discovered in several human pathogens that were long thought to be asexual, but so far there is no compelling evidence that it plays an important genetic role in their adaptation. The self-compatible (homothallic) sexual systems of many fungi severely limit their potential for recombination, but increase the rate at which they can segregate new adaptive mutations into homozygotes, a possible benefit of sex that has received much less attention than recombination.