Global urban environmental change drives adaptation in white clover

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Urbanization transforms environments in ways that alter biological evolution. We examined whether urban environmental change drives parallel evolution by sampling 110,019 white clover plants from 6169 populations in 160 cities globally. Plants were assayed for a Mendelian antiherbivore defense that also affects tolerance to abiotic stressors. Urban-rural gradients were associated with the evolution of clines in defense in 47% of cities throughout the world. Variation in the strength of clines was explained by environmental changes in drought stress and vegetation cover that varied among cities. Sequencing 2074 genomes from 26 cities revealed that the evolution of urban-rural clines was best explained by adaptive evolution, but the degree of parallel adaptation varied among cities. Our results demonstrate that urbanization leads to adaptation at a global scale.


Plants adapt to city environments

Urban development alters the local environment, potentially driving rapid evolution. Santangelo et al. collected data on white clover populations from 160 cities to test for consistent responses to urban environments. They found that the production of an antiherbivore chemical defense increased with greater distance from the urban center in many cities. Genomic data suggest that this trend is adaptive, likely in response to lowered drought stress and herbivory pressure in urban centers. This study from the Global Urban Evolution Project provides evidence of widespread adaptation to urbanization. —BEL