Mammalian functional diversity and trait responses to anthropogenic and environmental factors across the contiguous USA

Ongoing urbanization and land transformation drive profound changes in ecosystems worldwide, with wildlife responding in myriad ways. Particularly, functional homogenization of wildlife communities due to these widespread changes may reduce biodiversity and urban ecosystem resilience. However, there are benefits of urbanization (e.g., increased resources and survival) for some mammal species, likely supported by corresponding traits that facilitate the exploitation of human-dominated landscapes. Using data collected simultaneously from 107 sites throughout the contiguous United States, we explored how urban development, agricultural development, and environmental factors affected mammalian functional diversity (i.e., richness, evenness, and divergence of effect traits) and mean species’ traits at two spatial scales. Although we expected that urbanization would lead to mammal community functional homogenization, we found that urban development was positively associated with functional richness at the camera-site and all three functional metrics at the camera-array scales, whereas environmental variables (i.e., primary productivity, temperature) were not associated with any functional diversity metric. Sampling locations with greater urban development were associated with mammals that had smaller average home ranges, smaller average body sizes, and decreased mean rates of carnivory and scavenging. Identifying the effects of anthropogenic development on ecosystem functioning, as mediated by species' traits, is crucial as urban landscapes continue to expand globally.