Caste evolution and ecology: a special worker for novel prey

Area of Science:

• Evolutionary biology
• Animal behavior
• Entomology

Background:

• Individual specialization is key to ant societies, but physical castes are rare.
• The evolution of genetic conditions for castes is known, but ecological drivers are unclear.

Purpose of the Study:

• Investigate ecological pressures selecting for exaggerated transport castes in army ants.
• Determine if novel prey drives the evolution of specialized castes.

Main Methods:

• Comparative analysis of load-transport efficiency across Eciton species.
• Experimental assessment of submajor specialization on non-ant prey.
• Phylogenetic analysis of Eciton lifestyle constraints.

Main Results:

• A mixed diet of large arthropods and ants in Eciton burchellii constrains transport efficiency.
• Eciton burchellii submajors are specialized for transporting non-ant prey.
• Phylogenetic constraints amplified selection for the submajor caste.

Conclusions:

• Novel prey tasks can select for specialized castes when alternative solutions are evolutionarily blocked.
• This study presents a new scenario for the evolution of physical castes.