Urban evolution

Urban evolution refers to the heritable genetic changes of populations in response to urban development and anthropogenic activities in urban areas. Urban evolution can be caused by mutation, genetic drift, gene flow, or evolution by natural selection. Biologists have observed evolutionary change in numerous species compared to their rural counterparts on a relatively short timescale. Strong selection pressures due to urbanization play a big role in this process. The changed environmental conditions lead to selection and adaptive changes in city-dwelling plants and animals. Also, there is a significant change in species composition between rural and urban ecosystems. Shared aspects of cities worldwide also give ample opportunity for scientists to study the specific evolutionary responses in these rapidly changed landscapes independently. How certain organisms (are able to) adapt to urban environments while others cannot, gives a live perspective on rapid evolution. With urban growth, the urban-rural gradient has seen a large shift in distribution of humans, moving from low density to very high in the last millennia. This has brought a large change to environments as well as societies. Urbanization transforms natural habitats to completely altered living spaces that sustain large human populations. Increasing congregation of humans accompanies the expansion of infrastructure, industry and housing. Natural vegetation and soil are mostly replaced or covered by dense grey materials. Urbanized areas continue to expand both in size and number globally; in 2018, the United Nations estimated that 68% of people globally will live in ever-larger urban areas by 2050. Urbanization intensifies diverse stressors spatiotemporally such that they can act in concert to cause rapid evolutionary consequences such as extinction, maladaptation, or adaptation. Three factors have come to the forefront as the main evolutionary influencers in urban areas: the urban microclimate, pollution, and urban habitat fragmentation.