Developing a new metric to quantify the potential impacts of chemicals on the genetic makeup of wild populations

Chemical pollution threatens within-species genetic variation, and understanding this impact is essential to determine the adaptation potential of different species. However, genetic diversity has been reported to receive the least attention of the three levels of biodiversity outlined by the Convention of Biological Diversity, and while the field of evolutionary toxicology was proposed over a decade ago to help characterize the relationship between chemical exposures and genetic composition of wild populations, this relationship is still under-explored. To overcome challenges in experimentally testing impacts of the multiple chemicals in circulation on the genetics of many species, we propose that data-driven predictive approaches are essential. There is growing data from chemical monitoring/modelling to describe chemical concentrations globally, and wild populations are increasingly sampled for varied purposes (e.g., population genetics). We propose that integrating these published data to assess chemical impacts on the genetics of wild populations can provide insight into the susceptibility and adaptation potential of populations and species exposed to chemicals. As a proof of concept, we demonstrate the development of a new metric to assess and predict the concentration of pesticides that may alter the genetic makeup of wild populations. By relating modeled environmental soil concentrations of 92 pesticides to wild genetics data for several species in Europe (e.g., polyommatus icarus, caenorhabditis elegans, sus scrofa) with landscape genetics methods, we identify single nucleotide polymorphisms (SNPs) that differ in populations exposed to low or high concentrations of each pesticide. Then, we quantify the overall potential genetic impacts of each pesticide on each species individually and together using a new unified metric, similar to the methods for species sensitivity distribution but with the genetic impacts on each species as the endpoint. We propose that this new metric can serve as a complement to well-established metrics for chemical risk assessment (e.g., comparing the concentration of chemical affecting the genetic makeup in 5% of species as determined through our metric to the concentration affecting 5% of species on a species sensitivity distribution).