Innovation in ant larval feeding facilitated queen-worker divergence and social complexity

Area of Science:

• Evolutionary biology
• Insect social behavior
• Comparative genomics

Background:

• Multicellular organisms face challenges in developing distinct cell types from genetically identical units.
• In ants, larval feeding by adults determines caste (reproductive or worker), with significant variation across species.
• Phenotypic divergence between queen and worker castes is closely linked to larval care strategies.

Purpose of the Study:

• To investigate the evolutionary links between larval feeding care, caste size dimorphism, and social complexity in ants.
• To understand how changes in larval development influence the diversification of ant societies.
• To explore the role of parental care in shaping social evolution across ant diversity.

Main Methods:

• Comparative phylogenetic analyses across ant diversity.
• Causal inference modeling to establish relationships between traits.
• Digitization of larval morphology data for over 700 ant species.
• Compilation of data on ant diets, larval feeding behaviors, caste dimorphism, colony size, and worker reproduction.

Main Results:

• Ancestral active-feeding larvae developed passive morphologies with the advent of individual adult feeding, often with processed food and non-predatory diets.
• Increased queen-worker size dimorphism correlated with larval passiveness and traits of social complexity (larger colonies, worker subcastes, reduced worker reproduction).
• Phylogenetic models support that extended alloparental care promoted caste dimorphism, which, with larger colony sizes, enhanced social complexity.

Conclusions:

• Enhanced adult control over larval development facilitated greater phenotypic specialization within ant colonies.
• This specialization played a crucial role in the evolution of complex ant societies.
• The findings offer insights into the broader implications of developmental control for social evolution in nature.