Linear relationships between the proportion of non-native relative to native species in urban forests and each variable while controlling for variables in the other panels A the proportion of non-native to native species was not related to the area of urban islands, calculated in meters squared B the proportion of non-native to native species was not related to distance between the urban island and the unfragmented forest, calculated in meters C the proportion of non-native to native species increased with newer constructions D the proportion of non-native to native species increased with distance from the closest road, calculated in meters.