Cooperation-mediated plasticity in dispersal and colonization.

Area of Science:

• Evolutionary biology
• Behavioral ecology
• Microbial evolution

Background:

• Kin selection theory posits cooperation evolves with relatedness.
• Dispersal's role in cooperation is debated due to effects on relatedness and competition.
• Conditional dispersal strategies may resolve cooperation-dispersal conflicts.

Purpose of the Study:

• To experimentally test if dispersal decisions are mediated by cooperative strategy.
• To investigate density-dependent dispersal and colonization in Tetrahymena thermophila strains with varying aggregation levels.
• To link cooperative tendencies to dispersal phenotypes and kin-cooperation.

Main Methods:

• Quantified density-dependent dispersal decisions in six Tetrahymena thermophila genetic strains.
• Assessed colonization efficiency from single cells or groups.
• Characterized dispersal phenotypes and aggregation levels (high, medium, low).

Main Results:

• Dispersal rate plasticity varied by aggregation level: negative density-dependence in high-aggregation strains, intermediate density-max dispersal in low-aggregation strains, and density-independence in medium-aggregation strains.
• Highly aggregative genotypes exhibited specialized long-distance dispersal phenotypes.
• Evidence of beneficial kin-cooperation during dispersal was found in highly aggregative genotypes.

Conclusions:

• Conditional dispersal strategies can resolve the conflict between cooperation and dispersal.
• Cooperative individuals may disperse long distances to avoid kin competition.
• Dispersal in small groups allows cooperative individuals to retain cooperation benefits.