Population dynamics and genome-wide selection scan for dogs in Chernobyl

Abstract

Natural and anthropogenic disasters can have long-lasting impacts on the genetics and structure of impacted populations. The 1986 Chernobyl Nuclear Power Plant disaster led to extensive contamination of the local environment and the wildlife therein. Several ecological, environmental, and genetic studies reported various effects of this disaster on animal, insect, and plant species; however, little work has been done to investigate the genetics of the free-breeding dogs that occupy the Chernobyl Exclusion Zone (CEZ). We define the population genetic structure of two groups of dogs that reside within the CEZ, one around the reactor site itself and another living within Chernobyl City. We found little evidence of gene flow and a significant degree of genetic differentiation between the two populations dogs, suggesting that these are two distinct populations despite occupying areas located just 16 km apart. With an FST-based outlier analysis, we then performed a genome-wide scan for evidence of directional selection within the dog populations. We found 391 outlier loci associated with genomic regions influenced by directional selection, from which we identified 52 candidate genes. Our genome scan highlighted outlier loci within or near genomic regions under directional selection, possibly in response to the multi-generational exposure faced. In defining the population structure and identifying candidate genes for these dog populations, we take steps towards understanding how these types of prolonged exposures have impacted these populations. Wildlife populations can be greatly affected by disasters, whether they are natural or man-made. Disasters that result in contamination or habitat destruction can result in population declines or influence wildlife adaptation to these adverse environmental changes. The Chernobyl nuclear power plant disaster released an enormous quantity of ionizing radiation into the surrounding environment. Abandonment of military and industrial facilities, as well as subsequent cleanup and remediation efforts, resulted in further environmental contamination by a variety of non-radioactive toxic metals, chemicals, and compounds. Earlier studies investigated local wildlife responses to some of these exposures. In this study, we address the impact of this disaster on the population structure of free-breeding dogs that live around the power plant and in the nearby city of Chernobyl. In particular, we use genetic approaches to understand how these two populations of dogs interact and their breed composition, so that we may begin to understand how these populations have adapted to over 30 years of exposure to this harsh environment. In this foundational study we determined that while the two local populations of dogs are separated by only 16 km, they have very low rates of interpopulation migration. We also detected genetic evidence that suggests that these population may have adapted to exposures faced over many generations. In future studies, we aim to determine if the genetic variation detected is indeed a biological response to enable survival after multi-generational exposures to radiation, heavy metals, organic toxins, or other environmental contaminants. In this way, we then understand how the impact of environmental catastrophes such as the Chernobyl nuclear disaster can influence animal populations.