Ant genomes point to mobile DNA as size driver

A team led by Adria LeBoeuf posted two PacBio HiFi ant genome assemblies on bioRxiv on Oct. 11, reporting BUSCO completeness of 99.2% and 98.3%.

Evidence grade: Early, because the Oct. 11 bioRxiv preprint is not yet peer reviewed. The study compares a 187-megabase Platythyrea mocquerysi genome with a 262-megabase Stigmatomma oregonense genome, linking much of the size gap to repeat DNA.

What the team built

The authors assembled and annotated genomes for two poneroid ants with unusual brood-feeding traits. Platythyrea mocquerysi, a Malagasy ant, has larvae that produce secretions eaten by adults. Stigmatomma oregonense, a North American “dracula ant,” feeds on larval haemolymph, the insect blood-like fluid, without killing the larvae, according to the preprint.

The Platythyrea mocquerysi assembly measured 187 megabases across 307 scaffolds, with an N50 of 5.26 megabases. N50 is a genome-contiguity measure: half the assembly is contained in scaffolds at least that long.

The Stigmatomma oregonense assembly was larger and more fragmented, at 262 megabases across 1,189 scaffolds, with an N50 of 0.84 megabases. The authors reported 10,860 protein-coding genes for Platythyrea mocquerysi and 12,354 for Stigmatomma oregonense.

Why it matters

These genomes are research infrastructure rather than a human-health finding. They give comparative genomics researchers a way to examine how DNA variation may relate to social-insect traits, including larva-to-adult feeding and brood-management strategies.

PacBio HiFi is a long-read sequencing method that generates highly accurate stretches of DNA. For organisms with repetitive regions, long reads can help assemble parts of the genome that shorter-read methods may leave unresolved.

The authors used BUSCO, a common completeness benchmark based on expected single-copy genes, to report 99.2% completeness for Platythyrea mocquerysi and 98.3% for Stigmatomma oregonense. Those figures suggest the assemblies captured most of the expected gene set for the comparison used in the preprint.

What the results suggest

The preprint says repeat content differed sharply between the two ants: 54.3% in Stigmatomma oregonense compared with a lower bound of 15.7% in Platythyrea mocquerysi. The authors attributed most of that difference to unclassified repeats that they identified as diverged transposable elements.

Transposable elements are DNA sequences that can move or copy themselves within genomes. Their expansion or loss can change genome size without necessarily adding new protein-coding genes.

In a comparison that included two additional poneroid genomes from related species, the authors said genome-size differences across the group were largely explained by transposable-element dynamics. They also reported expansions in several Amblyoponinae gene families, including carboxylesterases, serine proteases and lipid-metabolism genes.

Limits of the evidence

The work does not show that any specific gene expansion causes a feeding behavior. It identifies genomic resources and comparative patterns that can guide later studies.

The preprint also does not establish whether the observed transposable-element differences affect fitness, development or colony behavior. Those questions would require functional experiments or additional comparative datasets.

The authors declared no competing interest. The preprint listed funding from the International Human Frontier Science Program Organization and the Lundbeck Foundation.

The data and code link in the bioRxiv record points to Zenodo, and the preprint was posted under a CC-BY 4.0 International license.

Source: academic preprint, bioRxiv, Oct. 11, 2026