Non-native host plant availability and habitat preference promote butterfly expansion across urbanized environments

Offering novel ecological opportunities and being centers of introduction of non-native species, urban environments are hotspots of biological invasions. Yet, how specific features of urban environments and of colonizing non-native species interact to enable the successful invasion of a novel range often remains unclear. We here focus on this interaction in the Southern Small White butterfly ( Pieris mannii ) that recently invaded Central Europe and is strongly associated with urban habitats in the novel range. Quantifying the occurrence of a non-native ornamental host plant and performing mark–release–recapture and habitat preference experiments, we first demonstrate a high availability of larval food resources within urban habitats. Next, we show that the butterfly’s dispersal happens primarily within a home range delimited by the local urban area, but that the occasional movement among neighboring settlements must enable effective stepping-stone range expansion. Finally, we find that the species disperses preferentially into urban as opposed to surrounding semi-natural habitat, likely mediated by urban structural features. Overall, our results illustrate how anthropogenic resource opportunity tightly associated with urban environments, combined with a species’ intrinsic dispersal behavior, have promoted rapid range expansion across a vast novel range.