Invasive Californian death caps develop mushrooms unisexually and bisexually

Canonical sexual reproduction among basidiomycete fungi involves the fusion of two haploid individuals of different mating types, resulting in a heterokaryotic mycelial body made up of genetically different nuclei. Using population genomics data and experiments, we discover mushrooms of the invasive and deadly Amanita phalloides can also be homokaryotic; evidence of sexual reproduction by single, unmated individuals. In California, genotypes of homokaryotic mushrooms are also found in heterokaryotic mushrooms, implying nuclei of homokaryotic mycelia are also involved in outcrossing. We find death cap mating is controlled by a single mating type locus, but the development of homokaryotic mushrooms appears to bypass mating type gene control. Ultimately, sporulation is enabled by nuclei able to reproduce alone as well as with others, and nuclei competent for both unisexuality and bisexuality have persisted in invaded habitats for at least 17 but potentially as long as 30 years. The diverse reproductive strategies of invasive death caps are likely facilitating its rapid spread, suggesting a profound similarity between plant, animal and fungal invasions. The death cap mushroom Amanita phalloides is invading California but little is known about how it spreads through forests. Wang et al. discover that this fungus can develop mushrooms and sporulate without mating; the nuclei involved in unisexuality appear to have persisted in invaded habitats for decades.

Automated summary

The death cap mushroom Amanita phalloides can also undergo sexual reproduction through single individuals, which facilitates its rapid spread and demonstrates a profound similarity between the reproductive strategies of fungal invasions and plant/animal invasions.