Changes in reptile and amphibian communities across urbanization gradients in eastern North America

Urbanization is expected to alter animal communities, but few studies have generalized beyond patterns in individual cities. We used community-science data on reptiles and amphibians from 17 cities in North America to determine: 1) how species richness differs between cities and surrounding areas, 2) whether the degree of landcover change in cities vs. surroundings is related to the magnitude of change in species richness, 3) whether urban communities are more similar to each other or to their surrounding areas, and 4) what characteristics of reptile and amphibian species predict how sensitive they are to urbanization. We found that species richness tended to be somewhat lower (10-20%) in cities as compared to surrounding areas. For reptiles, the magnitude of decrease in richness appeared to be primarily related to the degree of change in impervious surface cover, whereas for amphibians these changes tracked differences in canopy cover. There was little evidence of urban homogenization- city communities tended to cluster with their surrounding areas rather than with other cities. For individual species, those that were less represented in observations from cities tended to be more dependent on canopy cover and on specialized breeding habitats such as streams or vernal pools. Our results suggest that cities are capable of supporting a relatively high richness of reptiles and amphibians. However, maintenance of this richness may require attention to habitat protection and restoration, particularly for less common aquatic habitats.