Pathogen evasion of social immunity

Area of Science:

• Evolutionary biology
• Animal behavior
• Microbiology

Background:

• Collective disease defense is crucial in social species.
• Pathogen adaptation to host immunity is a key evolutionary process.
• Social immunity, involving behaviors like grooming, protects groups from disease.

Purpose of the Study:

• To investigate how pathogens adapt to social immunity.
• To understand the evolutionary trade-offs in pathogen traits under social selection.
• To identify mechanisms by which pathogens evade collective immune responses.

Main Methods:

• Serial passage experiment with social insects and pathogenic fungi.
• Comparison of pathogen evolution with and without social immunity (grooming).
• Chemical analysis of fungal spores and experimental manipulation of key compounds.

Main Results:

• Pathogens under social immunity showed increased spore production but reduced virulence.
• Spores evolved to elicit a lower grooming response from caregivers.
• Reduced ergosterol levels in spores from social selection lines decreased detection by hosts.

Conclusions:

• Pathogens can adapt to social immunity by evolving to evade detection.
• Ergosterol acts as a cue for social immunity, and its reduction is an evasion strategy.
• This study reveals pathogen counter-adaptations to collective host defenses.