Invasive plants affect native plant pollination through pollinator-mediated cross-boundary effects

Invasive plants may facilitate or compete with native plants by changing the foraging behavior and/or abundance of shared pollinators. Such effects have been explored within single habitats; however, many pollinators are highly mobile and can cross ecological boundaries. Whether via shared pollinators, invasive plants affect native plants in neighboring habitats remains an open question. Here, we ask this question in a mosaic of 22 native-plant-dominated meadows on serpentine soil, embedded in a matrix of non-serpentine meadows. The non-serpentine meadows contain dense stands of two insect-pollinated invasive species: Vicia villosa, and Centaurea solstitialis . The serpentine meadows contain two common native species that co-flower and share pollinators with these invasives: Trifolium fucatum and Helianthus exilis , respectively. Across three years, we determined that the abundance ratio of each invasive species in the surrounding landscape to its co-flowering native species within focal patches was associated with decreased visitation rates, seed set, and functional importance in the plant-pollinator network for the native species. We conclude that invasive plants can have indirect, negative effects on native plants in neighboring habitats, via competition for shared pollinators.