Evidence of same-sex mating in nature

Cryptococcus neoformans is a major cause of fungal meningitis in predominantly immunocomprised individuals.

This fungus has two mating-types/sexes, and mating typically requires two individuals with opposite mating types. It had been a mystery why one mating type is overwhelmingly predominant in nature and how the capacity for sexual reproduction is maintained in a largely unisex population.

In an article published in PLoS Genetics, Xiaorong Lin and colleagues from Duke University Medical Center analyzed natural Cryptococcus diploid hybrid isolates containing two á alleles of different serotypic origins. Natural áADá hybrids that arose by fusion between two á cells of different serotypes (A and D) were identified and characterized, demonstrating that same-sex mating transpires in nature. Same-sex mating had been observed under laboratory conditions, but direct evidence for naturally occurring same-sex mating was lacking. This study provides the first evidence of this and sheds light on the genetic and environmental factors that play important roles in the evolution of the current population structure of this pathogenic fungus.