Free-ranging dogs living at the Chornobyl Nuclear Power Plant carry genomic signatures that point to directional selection rather than random mutation, according to research reported by Mirage News. The study compared the plant's dog population with dogs in Chornobyl City, roughly 10 miles away, and with free-breeding dogs from Eastern Europe and an isolated population on the Galápagos Islands. The findings were published in the journal Genes, with Megan Dillon of North Carolina State University's College of Veterinary Medicine as first author.
Why it matters
The work follows earlier research that found a striking genetic gap between two dog groups living only a short distance apart. That study showed the Chornobyl City dogs closely resembled dog populations in Russia, Poland and nearby regions, while the power plant dogs stood apart in regions tied to DNA repair. The new analysis set out to explain why: whether natural selection shaped the difference, or whether it arose from genetic drift — random changes that spread in small, isolated populations regardless of fitness. Understanding which force was at work could inform broader questions about how animals adapt to contaminated environments, the report states.
Two forces, one population
Directional selection is a pronounced form of natural selection in which a population as a whole moves toward a narrow set of advantageous traits, and it is typically linked to shifts in the environment. Genetic drift works differently: random genetic changes become common even when they offer no fitness benefit, and the effect is stronger in small, isolated groups, where such changes are more likely to be passed on. Drift can also erode diversity across the genome.
Dillon said the earlier work had left loose ends, noting that the two groups are geographically very close yet genetically very different, and that mutation did not account for the gap. The team then asked whether selection or drift better explained it, according to Mirage News.
To separate the effects of isolation from those of environment, the researchers compared genomic data from the two Chornobyl groups with data from Eastern European free-breeding dogs and the Galápagos dogs. The power plant population is small, but its effective population size did not differ markedly from that of the Chornobyl City dogs. The plant dogs also showed no sign of the reduced genetic variation that would be expected under drift. Genetically, they diverged significantly from other isolated populations, including the Galápagos dogs. The Chornobyl City dogs, by contrast, were genetically closer to the Galápagos population than to the dogs living at the plant nearby.
Over 100 sites flagged
The genomic analysis identified evidence of directional selection at more than 100 locations in the power plant dogs. Genes situated around those sites are involved in cancer development, DNA replication and repair, cell cycle functions and immune function, the report states.
Dillon cautioned that the team cannot say for certain the findings are directly confirmed as selection, but described the genomic signatures as suggestive of it. Looking deeper into those regions, she said, the genes participate in biologically relevant pathways that could help the dogs cope with exposure to toxicants in their environment.
Matthew Breen, Oscar J. Fletcher Distinguished Professor of Comparative Oncology Genetics at NC State's College of Veterinary Medicine and the study's corresponding author, addressed the intuition that life around Chornobyl must have left a mark. He said the consequence may not have extended to altering the dogs' genome for adaptation. Instead, the animals that survived the initial exposures may have carried underlying genetic diversity and variants conferring greater fitness. Breen called that idea speculation, adding that what happened exactly is unknown, but said the analysis was robust and turned up signatures of selection in biologically relevant regions.
Beyond Dillon and Breen, the contributors were Reade Roberts, associate professor of biology at NC State; Jennifer Betz, a doctor of veterinary medicine with Visiting Veterinarians International; Timothy Mousseau, professor of biological sciences at the University of South Carolina; and Norman Kleiman, associate professor of environmental health sciences at Columbia Mailman School of Public Health.
Watch for follow-up work testing whether the flagged regions translate into measurable biological advantages for the plant dogs, and for whether similar patterns turn up in other species living in the exclusion zone.
