Urban plants are more closely related and live shorter lives than plants in the countryside.
Cities in both, the US and Europe harbor more plant species than rural areas. However, plant species of urban areas are more closely related to each other and often share similar functions. Consequently, urban ecosystems should be more sensitive towards environmental impacts than rural ecosystems.
Using a newly established global plant trait database (TRY), they found that the typical spontaneous yard species is short-lived, fast-growing, produces small seeds, uses humans as dispersal vectors, and is adapted to high temperatures. (2012) Science News.