An urban evolved invasive plant tolerates experimental climate change

Societal Impact Statement Urbanization may drive invasive species evolution, resulting in greater invasion risks as global conditions change. We compared urban populations of the invasive Erigeron annuus in Zagreb, Croatia, to surrounding rural populations and found that urban‐evolved populations were more tolerant of experimental warming and drought than rural populations. These adaptive shifts suggest urbanized invaders possess traits that promote spread into hotter, drier regions under climate change, threatening agriculture, biodiversity, and human health. The findings highlight the urgency of monitoring and managing urban areas for invasive species and the need to develop policies to mitigate biosecurity threats posed by climate change‐adapted invaders. Summary Novel urban conditions are hypothesized to drive evolution of invasive species, and urban evolved invaders are predicted to be more tolerant of climate change. We tested these hypotheses with the invasive plant Erigeron annuus in Zagreb, Croatia. Urban study sites had lower soil moisture, were hotter, and had more impervious surface than rural sites. In a common garden experiment under control conditions, plants from urban populations produced significantly less biomass than populations from rural sites, suggesting urban population evolution towards a conservative growth strategy. Under experimental warming, drought, and warming + drought treatments, urban populations were unaffected or were less negatively affected by the simulated climate change treatments than rural populations. These differences tracked the urban–rural gradient, where invasive plant population tolerance to climate change treatments increased with the degree of urbanization at source sites. Our results indicate that an invasive plant evolved in response to urbanization, resulting in exaptations that enhanced tolerance to experimental climate change. Consequently, urbanized invaders may present greater invasion risks as surrounding regions become hotter and drier.