Global Urbanization Drives Phenotypic Change in Wildlife

Phenotypic change is greater in urbanized areas than in natural or nonurban anthropogenic areas, according to a study recently published in Proceedings of the National Academy of Sciences of the United States of America. This phenotypic change has a distinct urban signature comprised of different types of urban disturbance mechanisms.

Global urbanization has increased rapidly from the mid-20th to early 21st centuries. By 2050, an estimated 66% of the world’s population is expected to live in urban areas. Evidence supports the idea of urbanization as a driver of contemporary evolution; urbanization leads to changes in habitat structure and alterations in biotic interactions among wildlife (e.g., predation).

It is not yet clear whether the role of urbanization in contemporary evolution will ultimately affect human health and well-being in urban areas, particularly regarding food production and reduction of atmospheric carbon levels. According to the authors, though, “ecoevolutionary changes are occurring at an unprecedented pace.”

For the current study, the authors conducted a meta-analysis of 89 studies to identify an urban signature of phenotypic change and evaluate the phenotypic effects of 5 types of urban disturbance: social interaction, biotic interaction, habitat modification, heterogeneity, and novel disturbance. Overall, rates of phenotypic changes were highest within urbanized areas, supporting the idea of an urban signature of phenotypic change.

Social interactions, which increase with urbanization, were found to play a major role in the urban phenotypic signature. The authors mentioned human interactions with other species, such as selective harvest of a medicinal plant, as a driver of urban phenotypic change. Interestingly, distant interactions between humans and other species, including through trade, can also impact phenotypic change.

Biotic interactions were also identified as a major player in the urban phenotypic signature. The authors wrote that “urban development creates new opportunities and challenges for species competition and predation, both as exotic species are introduced and as invasive species migrate in.” In urban areas, species find new ways to interact with each other and distribute themselves.

The authors did not observe a major urban phenotypic impact of habitat modification. They believe this may have been due to the overrepresentation of studies in the meta-analysis reporting on the vagility—the ability to freely move and migrate—of migratory birds. The ability to migrate from an urbanized area may reduce phenotypic change.

Heterogeneity, which refers to varied aspects of diversity within an urban area (e.g., differential distribution of soil organic matter, species richness), was also not found to impact urban phenotypic change significantly. Typically, when urbanization changes how land is used, the species composition in the area is also altered, potentially driving urban phenotypic change.

Similarly, novel disturbances did not have a significant effect on urban phenotypic change. Several examples of novel disturbances that could drive phenotypic change in urban areas were mentioned, including changes in resource availability and ecosystem productivity.

The authors noted that urban-driven phenotypic changes can enhance an organism’s survival chances within an urban environment, as well as benefit human health and ecosystem sustainability. However, these changes can also have negative effects, such as resistance to pesticides and antibiotics.

Understanding these phenotypic changes and their impact on ecosystems will, as the authors wrote, “provide insights for maintaining ecosystem function in the long term and can direct policy makers toward sustainability solutions.”

Dr. Pendergrass received her doctorate in veterinary medicine from the Virginia-Maryland College of Veterinary Medicine. Following veterinary school, she completed a postdoctoral fellowship at Emory University’s Yerkes National Primate Research Center. Dr. Pendergrass is the founder and owner of JPen Communications, LLC.