Compatibility groups in Ascobolus immersus - an indication of speciation

Area of Science:

• Mycology and Evolutionary Biology
• Reproductive Biology of Fungi

Background:

• Understanding fungal mating patterns is crucial for comprehending reproductive isolation and speciation.
• Ascobolus immersus serves as a model organism for studying genetic incompatibility mechanisms.

Purpose of the Study:

• To determine the mating patterns and compatibility groups of Ascobolus immersus strains from Europe and Southern India.
• To investigate the role of homogenic and heterogenic incompatibility in reproductive isolation and potential speciation.

Main Methods:

• Collection of 38 Ascobolus immersus strains from diverse geographical locations (Europe and Southern India).
• Controlled mating experiments to assess sexual reproduction and offspring viability between different strains and compatibility groups.
• Observation of intergroup crossing outcomes, including fertile offspring production and sterile fruit body formation.
• Analysis of barrage-like phenomena as indicators of further subdivision or incompatibility.

Main Results:

• Three distinct compatibility groups were identified: Group A (23 European strains), Group B (9 European strains), and Group C (6 Indian strains).
• Homogenic incompatibility controls sexual reproduction within each group.
• Heterogenic incompatibility prevents fertile offspring in intergroup crossings, indicating genetic separation.
• European Group B shows closer relation to Indian Group C, evidenced by sterile fruit body production.
• Barrage-like phenomena observed across all groups suggest potential for further subdivision.

Conclusions:

• Spatial and genetic isolation contribute to the initiation of speciation in Ascobolus immersus.
• The identified compatibility groups and incompatibility mechanisms provide insights into the evolutionary divergence of fungal populations.
• Ascobolus immersus demonstrates a dynamic interplay of isolation factors driving early-stage speciation.