# Population genomics of the Anthropocene: urbanization is negatively associated with genome-wide variation in white-footed mouse populations

## TL;DR

Urbanization reduces genetic diversity in small mammals, limiting their ability to evolve in changing environments.

## Contribution

This is the first study to quantify urbanization's impact on genome-wide variation and evolutionary potential in small mammals.

## Key findings

- Genome-wide variation decreases with increasing urbanization as measured by impervious surface cover.
- Urban populations show stronger genetic differentiation and deviation from global allele frequencies.
- Isolation by resistance models based on urban features better explain genetic differentiation than isolation by distance.

## Abstract

Urbanization results in pervasive habitat fragmentation and reduces standing genetic variation through bottlenecks and drift. Loss of genome-wide variation may ultimately reduce the evolutionary potential of animal populations experiencing rapidly changing conditions. In this study, we examined genome-wide variation among 23 white-footed mouse (Peromyscus leucopus) populations sampled along an urbanization gradient in the New York City metropolitan area. Genome-wide variation was estimated as a proxy for evolutionary potential using more than 10,000 SNP markers generated by ddRAD-Seq. We found that genome-wide variation is inversely related to urbanization as measured by percent impervious surface cover, and to a lesser extent, human population density. We also report that urbanization results in enhanced genome-wide differentiation between populations in cities. There was no pattern of isolation by distance among these populations, but an isolation by resistance model based on impervious surface significantly explained patterns of genetic differentiation. Isolation by environment modeling also indicated that urban populations deviate much more strongly from global allele frequencies than suburban or rural populations. This study is the first to examine loss of genome-wide SNP variation along an urban-to-rural gradient and quantify urbanization as a driver of population genomic patterns.