Genetic basis for queen-worker dimorphism in a social insect

Area of Science:

• * Social insect biology
• * Genetics and evolutionary biology
• * Behavioral ecology

Background:

• * Eusocial insects exhibit reproductive division of labor, cooperative brood care, and sterile worker castes.
• * Caste determination in females (workers vs. queens) is widely believed to be environmentally controlled.
• * The red harvester ant, *Pogonomyrmex barbatus*, serves as the model organism for this study.

Purpose of the Study:

• * To investigate the genetic underpinnings of caste determination in *Pogonomyrmex barbatus*.
• * To challenge the prevailing environmental model of caste determination in eusocial insects.
• * To propose a genetic model for caste determination involving linked loci.

Main Methods:

• * Analysis of microsatellite loci in *Pogonomyrmex barbatus* individuals.
• * Correlation of genotypes at a specific microsatellite locus with caste assignment (worker or queen).
• * Hypothesis formulation based on linkage disequilibrium between the microsatellite locus and putative caste-determining loci.

Main Results:

• * An individual's genotype at a specific microsatellite locus predicts its caste.
• * This microsatellite locus is in tight linkage disequilibrium with a caste-determining locus.
• * A genetic model proposes caste determination through distinct genetic lineages and heterozygosity/homozygosity at the caste locus.

Conclusions:

• * Caste determination in *Pogonomyrmex barbatus* has a significant genetic basis, contrary to environmental assumptions.
• * The proposed genetic model involves two lineages, with workers being heterozygous and queens homozygous at the caste locus.
• * This genetic system has implications for female multiple mating, sex ratio control, and reproductive allocation in social insects.