# Multi‐Omic Analysis Reveals Population Differentiation and Signatures of Social Evolution in Tetragonula Stingless Bees

## TL;DR

This study uses genomic data from Tetragonula stingless bees to explore how social evolution leaves distinct genetic signatures.

## Contribution

The paper presents a novel multi-omic analysis of social evolution in Tetragonula bees, revealing population differentiation and genomic signatures of social adaptation.

## Key findings

- Tetragonula carbonaria has three distinct populations, while T. hockingsi has two partially differentiated subpopulations.
- Worker-biased genes show higher nucleotide diversity and greater interspecies divergence than queen-biased genes, supporting a model of relaxed selection.
- Caste-biased genes differ in length, GC content, and evolutionary origin, aligning with patterns in other social insects.

## Abstract

Stingless bees in the genus Tetragonula are social insects with a fully sterile worker caste, and are therefore well‐placed to provide insights into the genomic changes associated with ‘superorganismal’ life histories. Here we assemble the genome of
Tetragonula carbonaria
and characterise the population structure and divergence of both
T. carbonaria
and its cryptic congener
T. hockingsi
in eastern Australia, revealing three distinct populations for
T. carbonaria
and two partially differentiated subpopulations for
T. hockingsi
. We then combine our genomic results with RNA‐seq data from different
T. carbonaria
castes (queens, males, workers) to test two hypotheses about genomic adaptations in social insects: the ‘Relaxed Constraint’ hypothesis, which predicts indirect, and therefore relaxed, selection on worker‐biased genes; and the ‘Adapted Worker’ hypothesis, which predicts intensified positive selection on worker genes due to their evolutionarily novel functions. Although we do not find a direct signal of either weaker purifying selection or elevated positive selection in worker‐biased genes based on deviations from neutral expectations of nucleotide change between the two species, other evidence does support a model of relaxed selection on worker‐biased genes: such genes show higher nucleotide diversity and greater interspecies divergence than queen‐biased genes. We also find that differentially caste‐biased genes exhibit distinct patterns of length, GC content and evolutionary origin. These findings, which converge with patterns found in other social insects, support the hypothesis that social evolution produces distinct signatures in the genome. Overall, Tetragonula bees emerge as a valuable model for studying the genomic basis of social complexity in insects.