Transcriptomic correlates of nutritional manipulation in a facultatively social bee

Area of Science:

• Insect behavior
• Evolution of cooperation
• Neurogenetics

Background:

• Subsocial behavior in insects involves parental care and can drive cooperation evolution.
• Nutritional manipulation of offspring can influence gene regulation and offspring size, potentially coercing cooperation.
• The eastern small carpenter bee (Ceratina calcarata) exhibits dwarf eldest daughters (DEDs) that are under-provisioned and act as foragers.

Purpose of the Study:

• To investigate if nutritional manipulation of DEDs alters brain gene expression.
• To understand the genetic basis of cooperative sibling care in Ceratina calcarata.
• To determine the relationship between body size, gene expression, and the emergence of subordinate behaviors.

Main Methods:

• Transcriptomic analysis of whole bee heads.
• Comparison of gene expression between naturally provisioned DEDs, regular daughters, experimentally under-provisioned daughters, and supplemented DEDs.
• Analysis of gene expression as a function of continuous body size.

Main Results:

• Minimal differences in gene expression were observed between groups.
• Gene expression varied dramatically with continuous body size, not discrete castes or order of eclosion.
• Gene Ontology (GO) term enrichment indicated hormonal regulation in smaller bees.

Conclusions:

• Differences in gene expression are primarily linked to absolute body size rather than nutritional status or caste.
• Hormonal regulation of transcription factors likely underlies behavioral differences observed in DEDs.
• Subordinate behaviors in DEDs may result from social environment and experience acting on body size and gene expression.