In the silent evolutionary race unfolding in our cities, Lasius niger has a hidden advantage written in its genes.
Imagine a world where your success depends on your ability to withstand toxic chemicals, repair damaged DNA, and radically change your diet and communication methods. This is not a science fiction scenario but the reality for the black garden ant, Lasius niger, as it conquers urban environments across Europe and beyond. Recent genomic research has uncovered the extraordinary genetic preadaptations that allow this tiny insect to thrive in our concrete jungles while other species disappear.
In evolutionary biology, preadaptation refers to the possession of characteristics that happen to be advantageous when an organism faces new environmental conditions. These traits did not originally evolve for their current purpose but through a process called exaptation, they are co-opted for new functions that enable survival in changing ecosystems.
For the black garden ant, certain genetic features that evolved for life in natural environments have proven surprisingly useful for navigating the unique challenges of urban habitats. This fortunate coincidence has transformed Lasius niger from a forest-dwelling species into what scientists call "the most successful urban inhabitant of all ants" 1 2 .
Urban environments present numerous obstacles for small organisms:
From pesticides, vehicle emissions, and industrial waste
That isolates populations
That disrupts natural rhythms
Causing elevated temperatures
These stressors would spell doom for many species, yet Lasius niger not only survives but thrives under these conditions. Researchers have observed this species "increasing its abundance in highly affected territories" while other ants disappear 2 . The secret to this remarkable success lies buried in the ant's genetic blueprint.
In 2017, researchers achieved a significant milestone: sequencing the draft genome of Lasius niger. Through sophisticated analysis comparing this genome to those of other ant species, scientists began identifying the unique genetic features that enable urban adaptation 1 2 .
Contigs in the genome assembly
Total genome length
CYP9 genes (vs. fewer in other ants)
One of the most dramatic discoveries was the expansion of the CYP9 cytochrome family 1 2 7 . Researchers found 19 complete and 21 nearly complete CYP9 genes in Lasius niger – over twice as many as in other ant species 1 2 .
These cytochrome P450 enzymes play crucial roles in breaking down toxic substances. The study discovered eleven positively selected positions in ligand-binding pockets of these enzymes, indicating strong directional selection has shaped these proteins for optimal function 1 2 . Originally, this expansion might have represented a defense mechanism against mycotoxins produced by Fusarium fungi 7 . In urban environments, these same enzymes likely provide resistance to human-made pollutants and pesticides 1 7 .
The urban environment exposes organisms to increased DNA-damaging agents. Remarkably, the predicted proteome of Lasius niger is "significantly enriched relative to other ant genomes in terms of abundance of domains involved in nucleic acid binding, DNA repair, and nucleotidyl transferase activity" 1 2 .
This proliferation of DNA repair systems appears to be a genomic response to transposable element proliferation – essentially, the ant genome has developed better mechanisms to maintain genetic stability in challenging conditions 1 2 .
In a surprising finding, researchers detected gene family contraction for several components of the olfactory system 1 2 . This reduction in odorant receptors and binding proteins was accompanied by "instances of both directional selection and relaxation" 1 2 .
In nutrient-poor urban environments, maintaining complex chemical communication systems may be energetically costly. By reducing investment in these systems, urban ants may reallocate resources to more critical functions, though the exact adaptive significance remains under investigation.
To understand how urban and rural ants differ at the genetic level, researchers conducted a sophisticated comparison of Lasius niger populations from Moscow city and natural habitats in Moscow oblast 4 .
"SNP frequencies are significantly different in 64 genes according to Fisher's exact test," with many of these genes "affected by recent selection" 4 .
The discovery that genes influencing retrotransposon mobility are under selection suggests that urban environments may increase genomic instability, driving adaptation through transposable element activity 4 .
| Genetic Category | Findings | Potential Adaptive Significance |
|---|---|---|
| Retrotransposon Genes | 26 of 64 genes with different SNP frequencies encoded retrotransposon proteins 4 | Possible response to environmental stress |
| Immune Response Genes | Differences in genes for viral and fungal infection defense 4 | Adaptation to urban pathogens |
| Hippo/Fat Pathway Elements | Significant differences in these developmental genes 4 | Potential changes in growth patterns |
| RNA Polymerase II Regulators | Repressors and mediators showed population differences 4 | May influence retrotransposon mobility |
Beyond genetic changes, Lasius niger displays remarkable behavioral flexibility that complements its genomic preadaptations:
Recent research has documented that night warming (NW) and artificial light at night (ALAN) increase nocturnal foraging activity in urban Lasius niger 3 . Urban colonies also show reduced aggression compared to their forest counterparts, a behavioral pattern observed in other urban ant species as well 8 .
This behavioral shift allows urban ants to exploit the 24-hour foraging opportunities presented by cities, giving them a competitive advantage over species that remain strictly diurnal.
Urban environments present different nutritional challenges. Studies comparing urban and rural colonies found that urban ants have less access to high-quality carbohydrates and "tend to consume less protein and fat" 5 . This nutritional stress manifests in lower body fat content in female sexuals (gynes) from urban populations 5 .
Despite these nutritional constraints, urban colonies persist and grow, suggesting they have developed strategies to cope with reduced food quality.
| Trait | Urban Populations | Rural Populations |
|---|---|---|
| Detoxification Genes | Expanded CYP9 family (19-21 genes) 1 2 | Smaller CYP9 family |
| DNA Repair Systems | Enhanced and diversified 1 2 | Standard for ants |
| Olfactory System | Reduced complexity 1 2 | More developed |
| Foraging Pattern | Increased nocturnal activity 3 | Primarily diurnal |
| Colony Nutrition | Lower quality diet, lower fat in reproductives 5 | Higher quality diet |
| Aggressiveness | Less aggressive (based on related species) 8 | More aggressive |
Understanding urban adaptation in ants requires sophisticated laboratory techniques and technologies:
Population genetic analysis from pooled samples
Identifying selection signatures 4
The black garden ant's success story reveals a profound evolutionary truth: sometimes survival depends not on developing entirely new adaptations, but on creatively using what already exists. As one research team concluded, "the success of L. niger in urbanized areas may be the result of fortuitous coincidence of several factors," including cytochrome expansion, DNA repair diversification, and olfactory reduction 1 2 .
Through genomic exaptation, Lasius niger has transformed potential vulnerabilities into strengths, writing a new chapter in the evolutionary playbook – one where ancient genes find new purposes in the concrete landscapes of the Anthropocene. As cities continue to expand, understanding these evolutionary processes becomes increasingly crucial for conserving biodiversity in our urbanizing world.
The humble black garden ant reminds us that even in our most engineered environments, natural selection continues to shape life, finding innovative solutions to the novel challenges of urban existence.