Group-selection via aggregative propagule-formation enables cooperative multicellularity in an individual based,...

Area of Science:

• Evolutionary Biology
• Theoretical Biology
• Ecology

Background:

• Multicellularity evolved multiple times, with aggregative multicellularity involving cooperation among potentially unrelated lineages.
• Maintaining cooperation against non-contributing 'cheater' phenotypes is a key challenge in aggregative multicellularity.
• Spatial structure and environmental heterogeneity are hypothesized to promote cooperation and group selection.

Purpose of the Study:

• To investigate the role of spatiality and predation in maintaining aggregative multicellularity.
• To determine if aggregation facilitates the survival of cooperators in temporally heterogeneous environments against cheaters.
• To evaluate the necessity and sufficiency of predation for the stability of aggregative multicellularity.

Main Methods:

• Individual-based modeling on an ecological timescale.
• Simulation of temporally heterogeneous environments with periodic colonization.
• Comparison of different population reproduction modes with and without individual selection (predation).

Main Results:

• In homogeneous environments without dispersal, cheaters invariably dominate.
• Predation can aid cooperators but is insufficient alone to maintain their proportion during dispersal.
• Aggregation-based propagation effectively maintains the cooperator-to-cheater ratio, even without predation.

Conclusions:

• Spatiality and temporal heterogeneity, through group selection, are crucial for maintaining aggregative multicellularity.
• While predation may facilitate aggregation, it is neither necessary nor sufficient for the long-term stability of aggregative multicellularity.
• Effective group selection mechanisms, particularly aggregation-based propagation, are key to the persistence of cooperative groups.