Urbanization is a major cause of biotic homogenization and habitat fragmentation for native communities. However, the role of urbanization on the success of biological invasions on a continental scale has yet to be explored. Urbanization may facilitate the establishment success of invasive species by minimizing niche differentiation between native and invaded ranges. In such cases, we might expect anthropogenic variables to have stronger influence on the geographic distribution of invasive compared to native populations. In this study, we use ecological niche modeling to define the distribution of non-native brown widow spider (Latrodectus geometricus) and three native black widows (L. hespersus, L. mactans, L. variolus) in North America and gauge the importance of urbanization on the geographic ranges of widows at a continental scale. We also quantify the geographic overlap of L. geometricus with each native widow to assess potential species and regions at risk of ecological impact. Consistent with our hypothesis, we find that the distribution of L. geometricus is strongly constrained to urban environments, while native widow distributions are more strongly driven by climatic factors. These results show that urbanization plays a significant role in facilitating the success of invasion, weakening the significance of climate on the realized niche in its invaded range.

Highlights• We estimate climatic niche overlap between widow spiders in North America, assess potential competition between native and invasive species, and evaluate the historical niche dynamics among native widows• Occurrence data used for modeling climatic niches include 25 occurrences of L. geometricus from community submissions on social media• Invasive L. geometricus and native widows have strongly overlapping climatic niches compared to native species among each other.• This study shows niche differentiation between morphologically cryptic L. hesperus and L. mactans, and potential for negative competitive interactions between invasive and native species, given strong climatic and geographic niche overlap.