%0 Journal Article %A C. Schmidt %A M. Domaratzki %A R.P. Kinnunen %A J. Bowman %A C.J. Garroway %T Continent-wide effects of urbanization on bird and mammal genetic diversity %D 2019 %R 10.1101/733170 %J bioRxiv %P 733170 %X Urbanization and associated environmental changes are causing global declines in vertebrate populations. In general, population declines of the magnitudes now detected should lead to reduced effective population sizes for animals living in close proximity to humans. This is cause for concern because effective population sizes set the rate of genetic diversity loss due to genetic drift, the rate of increase in inbreeding, and the efficiency with which selection can spread beneficial alleles. We predicted that the effects of urbanization should decrease effective population size, which would in turn decrease genetic diversity and increase population-level genetic differentiation. To test for such patterns, we repurposed and reanalyzed publicly archived genetic data sets for North American birds and mammals. After filtering, we had usable raw genotypes for 41,023 individuals, sampled from 1,008 locations spanning 41 mammal and 25 bird species. We used census-based urban-rural designations, human population density, and the Human Footprint Index as measures of urbanization and habitat disturbance. As predicted, mammals sampled in more disturbed environments had lower effective population sizes and genetic diversity, and were more genetically differentiated from those in less disturbed environments. There were no consistent effects for birds. This suggests that mammal populations continuing to live in close proximity to humans can generally be expected to have less capacity to respond to further environmental changes, and more likely to suffer from effects of inbreeding.Significance statement The leading cause of contemporary biodiversity loss at the level of populations and species is the wholesale transformation of natural environments by humans. In the span ∼50 years vertebrate populations have declined by ∼60% on average while the number of threatened and endangered species has increased. These systematic reductions in population size will likely have unintended effects on evolutionary change in animals. Here, we show that environmental degradation consistently erodes the genetic diversity of mammal populations living in close proximity to humans in ways that negatively affect their probability of persistence, compounding direct effects of habitat loss. %U https://www.biorxiv.org/content/biorxiv/early/2019/08/13/733170.full.pdf