Species-specific responses to roads and urbanization predict invasion of wetlands by non-native plants in the Chicago, Illinois region

In urban areas human modification of the landscape, including land development, road construction and species import, has facilitated the spread of non-native species. The effects of urbanization are likely to be species specific and an understanding of these species-specific responses is needed to assist management of non-native species. We examined the influence of urbanization and roads on the occurrences of 16 non-native plant species in over 2000 wetlands within the Chicago region in northeastern Illinois. Our primary objective was to determine whether landscape context, road characteristics, distance among wetlands, or a combination of those variables best predicted occurrences of selected species. Our study species included a group of halophytes, which we expected to be associated with major roads where de-icing salt is applied at higher rates. We also expected that non-native species would occur more frequently as the amount of urban land cover increased and proximity to the city of Chicago decreased. Species occurrences were modeled using multiple logistic regression with model selection based on an information theoretic approach.