Invasive Californian death caps develop mushrooms unisexually and bisexually

Area of Science:

• Mycology
• Invasive Species Biology
• Population Genomics

Background:

• Basidiomycete fungi typically reproduce sexually through the fusion of two haploid individuals.
• This process results in a heterokaryotic mycelium composed of genetically distinct nuclei.
• The invasive and deadly death cap mushroom (Amanita phalloides) is a key subject in fungal reproduction studies.

Purpose of the Study:

• To investigate the reproductive strategies of the invasive death cap mushroom (Amanita phalloides).
• To determine if homokaryotic (single-nucleus) mushrooms can arise from single, unmated individuals.
• To understand the genetic control and ecological implications of diverse reproductive modes in invasive fungi.

Main Methods:

• Population genomics analysis of invasive Amanita phalloides populations.
• Experimental studies to observe and confirm reproductive behaviors.
• Genotyping of homokaryotic and heterokaryotic mushrooms to infer nuclear interactions.

Main Results:

• Discovery of homokaryotic mushrooms in Amanita phalloides, indicating reproduction by single individuals.
• Evidence suggests homokaryotic nuclei also participate in outcrossing within heterokaryotic mushrooms.
• Mating in death caps is controlled by a single mating type locus, but homokaryotic mushroom development bypasses this control.
• Nuclei capable of both unisexuality and bisexuality have persisted in invaded areas for 17-30 years.

Conclusions:

• Amanita phalloides exhibits diverse reproductive strategies, including unisexual reproduction, which likely facilitates its rapid spread.
• The ability of nuclei to reproduce both alone and with others contributes to the success of this invasive fungus.
• This reproductive flexibility in fungi mirrors successful invasion strategies seen in plants and animals.