Pollinator conservation paradox: exotic wildflowers support native pollinators under global changes

Invasive wildflowers pose a conservation paradox: while they often reduce the diversity and abundance of native wildflowers, they can provide resources for native pollinators, including imperiled species. Previous work has framed wildflower invasions as outcomes of global change, but less is known about how interacting anthropogenic drivers influence both invasion and pollination. In particular, it remains unclear whether exotic wildflowers compensate for native floral losses under ongoing environmental change. To address this, we tested whether exotic wildflowers support native pollinators under two drivers of wildflower decline: eutrophication and defaunation. Using a factorial global change experiment at three sites in the highly invaded California floristic region, we tested whether increases in exotic wildflowers (1) sustain pollinator visitation and richness, (2) maintain pollinator composition and function, and (3) facilitate co-invasion by exotic pollinators. We found that eutrophication promoted exotic asters, which served as visually prominent, attractive hubs in plant-pollinator networks. These asters supported both generalist and specialist native pollinators but also increased visitation by exotic pollinators, raising the risk of invasional meltdown. Our results suggest that exotic wildflowers can buffer pollinator communities against global change, but may do so while shifting pollinator composition toward non-native species.