Intensity and duration of urbanisation drive adaptive divergence of functional traits and ecological strategies in Youngia japonica.

Urbanization affects plant adaptation because of the spatial distribution of impermeable surfaces and temporally persistent severe disturbances. However, how the duration of urbanization affects plant adaptation processes is unclear. We investigated the impact of urbanization intensity and duration on the functional traits and CSR (Competitor-Stress Tolerator-Ruderal) strategies of Youngia japonica. Urbanization significantly influenced plant height, leaf characteristics, flower diameter, decreased S-selection, and promoted R-selection. Populations from high and extreme urbanization areas with prolonged exposure demonstrated greater plant metrics and intraspecific C-selection, but lower R-selection, compared to those from areas with shorter exposure. Controlled common garden experiments corroborated these findings, revealing the highest C-selection and lowest R-selection under extreme urbanization. Similarly, populations from prolonged extreme urbanization had reduced plant height, leaf length, and specific leaf area after cultivation in common gardens. In situ measurements and common garden experiments showed that common garden populations in similar urban settings had notably larger leaf length, area, and weight compared to in situ populations. Areas with long-term extreme urbanization consistently selected for larger flowers across both environments. Additionally, populations exposed to prolonged urbanization exhibited more stable leaf and plant height characteristics. Conversely, those from shorter-duration urban environments demonstrated quicker trait recovery in common gardens. The level and duration of urbanization significantly influence the adaptive divergence in plant functional traits and ecological strategies. Extreme urbanization accentuates these differences, potentially leading to trait stabilization over time. Further research is needed to determine how different durations of urbanization affect ecological and evolutionary processes, which could advance the field of evolutionary ecology.