A conserved genetic switch for sex determination across 150 million years of evolution

A deeply conserved mechanism drives sex determination in one of Earth’s most diverse insect lineages.

Researchers have discovered a conserved genetic mechanism that controls sex determination in ants, bees, and hornets despite vast differences in their DNA sequences. Their findings suggest that a key sex-determination locus has remained functionally unchanged across more than 150 million years of evolution, challenging the long-held belief that such systems evolve rapidly and are unique to specific insect lineages. The findings open new avenues for understanding evolutionary biology, conservation, and the genetic basis of development.

Short overview

• Deep evolutionary conservation: The ANTSR locus has governed female development in ants, bees, and stinging wasps since over 150 million years ago. This represents one of the most ancient and stable sex-determining systems known in animals.
• Functional persistence without sequence similarity: Despite complete loss of detectable DNA sequence homology across species, the ANTSR locus maintains its function in sex determination. This challenges the long-held assumption that functional conservation requires sequence conservation.
• Function over form: While the DNA sequence itself has changed beyond recognition, the location of the ANTSR locus has remained a constant, acting like a genetic landmark that guides female development across species.

Sex determination in insects has long been thought to evolve rapidly, with master genes appearing and disappearing across lineages. But this study by Dr. Pan, now at the Max Planck Institute for Biology, and IMPRS student Chuanxin Yu with collaborators from Germany, France, Switzerland and China, reveals a rare exception: a conserved sex-determination locus that has remained functionally intact across ants, bees, and hornets despite vast evolutionary distances. The discovery was sparked by curiosity about the Argentine ant’s unique sex-determination system, which hinges on a long non-coding RNA called ANTSR. Only individuals with two different copies of the ANTSR locus develop into female

“We were fascinated by the evolutionary origin of a seemingly fragile system,” says Dr. Qiaowei Pan. “If this system is so special, could it be more widespread than we thought? And if so, could there be core sequences of functional unit that are conserved?”

To answer these questions, the team conducted a large-scale comparative genomics study across 41 hymenopteran species which includes ants, bees and wasps. They found that the genomic location and functional architecture have an ancient origin. This led them to test whether the same locus controls sex in other hymenopterans. Using genetic mapping in bumblebees and Asian hornets, they confirmed that this locus functions as the primary sex-determination switch across the entire group demonstrating functional conservation over an evolutionary timespan of approximately 150 million years.

Interestingly, no sequence similarity was detected at the ANTSR locus across species. This challenges the prevailing view that conserved function requires conserved DNA sequence. Instead, the study shows that genetic elements can maintain critical biological roles through structural or regulatory mechanisms that do not rely on sequence identity—a paradigm shift in how we identify and understand conserved genomic regions.

“This is a fascinating example where function persists without sequence,” says Pan. “It suggests that genetic elements can retain conserved functions through mechanisms other than primary DNA sequence, which is the prevailing basis for identifying conserved genomic elements.

The implications of this work are far-reaching. Hymenopteran insects are vital to ecosystems and economies as pollinators, biological control agents, and invasive species. The discovery of this broadly conserved sex-determination region provides a molecular tool for breeding and conservation programs. It enables scientists to monitor genetic diversity at the sex locus across populations of Aculeata (the group including ants, bees, and hornets), which is critical for preventing inbreeding depression and ensuring population viability.

“Loss of diversity at this locus leads to the production of non-viable males and population collapse,” explains Dr Pan “While the honeybee sex-determination locus was identified two decades ago and revolutionized our understanding of bee populations, it is evolutionarily young and limited to honeybees. Our discovery, however, applies to the vast majority of ants, bees, and hornets making it a game-changer for conservation.”