In the cracks of sidewalks and the soil of city parks, a tiny evolutionary drama is unfolding—one that's written in the language of genes.
You've likely seen them—lines of small, black ants marching determinedly across a pavement seam or tending to insect herds on a city plant. The black garden ant, Lasius niger, has become one of the most successful inhabitants of our urban landscapes. While many species struggle with urban pressures, these ants thrive thanks to a fascinating genetic preadaptation: the amplification of their CYP9 genes.
This story of adaptation isn't about learning new behaviors but rather about unleashing a hidden genetic potential that existed long before the first cities were built.
To understand what makes urban ants successful, scientists have turned to genomics—studying the entire genetic blueprint of organisms. By 2014, researchers had sequenced the genomes of eight ant species, looking for clues to their ecological success, caste differentiation, and social communication 1 .
What they discovered was striking: ants have significantly amplified their cytochrome P450 genes 1 . These genes produce enzymes that function as the cell's detoxification specialists, breaking down both internal substances and external toxins.
While the specific functions of many cytochrome P450 families were known, one family remained mysterious—the CYP9 family, which appeared to be particularly amplified in ants 1 . The question was: what were these genes doing, and could they hold the key to urban adaptation?
Among all ant species, the black garden ant stands out for its remarkable success in urban environments. In natural settings, Lasius niger typically occupies a subdominant position in ant communities 4 . Yet when forests make way for cities, the dominant ant species often disappear, creating opportunities for others 4 .
Lasius niger has not only filled these opportunities but flourished, becoming "the most successful urban inhabitant of all ants" 4 . Their secret lies in a combination of behavioral flexibility and—as researchers would discover—a special genetic toolkit.
In 2015, scientists made a breakthrough: by reading and annotating the Lasius niger genome, they discovered a significant expansion of CYP9 genes and used virtual screening to predict their functions 1 . The data suggested these cytochromes could metabolize various xenobiotics—foreign chemicals including phytotoxins from plants, mycotoxins from fungi, and synthetic insecticides 1 .
The most fascinating aspect of this discovery is that it represents preadaptation—the CYP9 expansions appear to have evolved initially as a response to natural toxins, particularly those produced by Fusarium fungi, rather than human-made chemicals 1 3 .
This evolutionary history meant that when Lasius niger encountered urban environments filled with pesticides and pollutants, they already possessed a detoxification system that could be co-opted for new purposes. Their genomic toolkit was already stocked with tools for new jobs.
Later research confirmed these findings, showing that the CYP9 family in Lasius niger is "highly expanded with 19 complete and 21 nearly complete members—over twice as many compared to other ants" 4 . Even more telling, these genes show signatures of strong directional selection, with eleven positively selected positions in the ligand-binding pockets of the enzymes—the very regions that determine what substances the enzymes can interact with 4 .
Genetic adaptations tell only part of the story. Recent research from 2024 reveals how urban living has shaped ant behavior as well. Scientists studying the protective mutualism between black garden ants and pink tansy aphids along an urbanisation gradient in Berlin made a remarkable discovery 6 .
While aphid colonies flourished equally across all environments, ants in more urbanized sites responded more aggressively to simulated attacks on their aphid partners 6 .
This increased defensiveness suggests that in cities, where resources may be scarcer and more unpredictable, ants rely more heavily on their mutualistic relationships and defend them more vigorously 6 .
Scientists used a variety of sophisticated tools and methods to uncover the genetic secrets of Lasius niger's urban adaptation:
| Research Tool | Primary Function | Example Use in Ant Research |
|---|---|---|
| Illumina Sequencing | Determines the order of DNA nucleotides | Generated 272M reads for Lasius niger genome assembly 4 |
| SPAdes Software | Assembles short DNA sequences into complete genomes | Assembled Lasius niger contigs from Illumina reads 4 |
| Virtual Screening | Computer-based prediction of molecular interactions | Predicted functions of CYP9 genes by simulating substrate binding 1 |
| AUGUSTUS | Predicts genes within genomic sequences | Identified protein-coding genes in the Lasius niger genome 4 |
| CRISPR-Cas9 | Precisely edits specific genes | Developed for Lasius niger to study gene function through modification 7 |
| BLAST Analysis | Compares sequences to databases for identification | Annotated predicted genes by comparing to known proteins 4 |
The success of Lasius niger in cities appears to be the result of several complementary factors:
Reduced reliance on complex odorant communication suits the patchy urban environment 4
Non-territorial foraging and efficient mobilization allow exploitation of scattered urban resources 4
This combination of genetic fortune and behavioral flexibility has made Lasius niger uniquely equipped to thrive in human-dominated landscapes.
The discovery of CYP9 amplification in ants offers insights that extend far beyond entomology. It demonstrates how preexisting genetic variations can become extraordinarily valuable when environments change rapidly—a phenomenon increasingly relevant in our era of global urbanization and climate change.
Understanding these adaptive mechanisms may help us predict which species will survive anthropogenic environmental changes and develop more targeted approaches to pest management that account for evolutionary adaptations.
The humble black garden ant reminds us that evolution doesn't always invent new solutions—sometimes it repurposes old ones in remarkably creative ways.
The next time you see a trail of ants navigating the urban jungle, remember: you're witnessing millions of years of evolutionary wisdom adapted to meet the challenges of our modern world.