Evolutionary transitions towards eusociality in snapping shrimps

Area of Science:

• Evolutionary biology
• Animal behavior
• Social evolution

Background:

• Animal social organization ranges from communal breeding to eusociality, where reproduction is monopolized.
• The evolutionary pathways leading to complex social structures remain poorly understood.
• Competing hypotheses propose eusociality and communal breeding as alternative endpoints or communal breeding as an intermediate stage.

Purpose of the Study:

• To investigate the evolutionary transition from simple to complex animal societies.
• To test whether eusociality and communal breeding are alternative endpoints or sequential stages in social evolution.
• To examine the social organization of sponge-dwelling shrimps (Synalpheus spp.) as a model system.

Main Methods:

• Comparative analysis of reproductive skew and demographic traits across Synalpheus spp.
• Development and application of evolutionary transition models.
• Phylogenetic analysis to infer evolutionary pathways.

Main Results:

• Synalpheus spp. exhibited a continuous variation in reproductive skew but clustered into distinct pair-forming, communal, and eusocial categories.
• Evolutionary models indicated that eusocial and communal species represent discrete evolutionary endpoints.
• These distinct paths originated independently from pair-forming ancestors.

Conclusions:

• Communal breeding and eusociality in shrimps are likely alternative evolutionary endpoints, not a linear progression.
• The 'family-centred' origin of eusociality in shrimps mirrors findings in insects and vertebrates.
• This suggests kin selection plays a crucial role in the evolution of eusociality, supporting a general model of animal social evolution.