Plant traits and extinction in urban areas: a meta-analysis of 11 cities

Aim Urban environments around the world share many features in common, including the local extinction of native plant species. We tested the hypothesis that similarity in environmental conditions among urban areas should select for plant species with a particular suite of traits suited to those conditions, and lead to the selective extinction of species lacking those traits. Location Eleven cities with data on the plant species that persisted and those that went locally extinct within at least the last 100 years following urbanization. Methods We compiled data on 11 plant traits for 8269 native species in the 11 cities and used hierarchical logistic regression models to identify the degree to which traits could distinguish species that persisted from those that went locally extinct in each city. The trait effects from each city were then combined in a meta-analysis. Results The cities fell into two groups: those with relatively low rates of extinction (less than 0.05% species per year - Adelaide, Hong Kong, Los Angeles, San Diego and San Francisco), for which no traits reliably predicted the pattern of extinction, and those with higher rates of extinction (> 0.08% species per year - Auckland, Chicago, Melbourne, New York, Singapore and Worcester, MA), where short-statured, small-seeded plants were more likely to go extinct. Main conclusions Our analysis reveals patterns in trait selectivity consistent with local studies, suggesting some consistency in trait selection by urbanization. Overall, however, few traits reliably predicted the pattern of plant extinction across cities, making it difficult to identify a priori the extinction-prone species most likely to be affected by urban expansion.