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ABSTRACT Nutrient enrichment has decreased the diversity and abundance of wildflower species, raising questions about whether nutrient enrichment can further decrease the diversity and abundance of pollinators that rely on wildflowers. Whether the effects of nutrient enrichment on plant–pollinator interactions differ by nutrient type remains an open question. Moreover, plant family and flower color, two core axes of pollination niches, may further mediate how wildflowers and their pollinators respond to nutrient enrichment. We tested these questions using a nutrient addition experiment replicated at three grasslands in California, a global plant diversity hotspot. We found that adding nitrogen increased the floral abundance of Asteraceae, while decreasing that of Fabaceae, Geraniaceae, Iridaceae, and Euphorbiaceae. Adding phosphorus and potassium in the absence of nitrogen produced the opposite effects. Pollinator abundance and composition varied strongly by floral family, suggesting that these differing responses to nutrient addition by floral family may alter pollinator community composition. Nitrogen addition decreased the abundance of native blue, native green, and exotic pink flowers, while increasing the abundance of native and exotic yellow and exotic purple flowers. Consequently, nitrogen addition increased pollinator abundance on purple flowers, while decreasing pollinator abundance on pink flowers. Purple and yellow Asteraceae species, which increased under nitrogen enrichment, acted as core hubs in structuring the plant–pollinator network.Synthesis:Our findings suggest that the type of nutrient, plant family, and flower color modulate how plant–pollinator interactions respond to eutrophication.
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This content will become publicly available on May 1, 2027
Pollinator conservation paradox: Exotic wildflowers provision native pollinators under anthropogenic changes
Abstract 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 provide resources for 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 attracted 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 anthropogenic change but may do so while shifting pollinator composition toward non‐native species.
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- Award ID(s):
- 2425352
- PAR ID:
- 10686814
- Publisher / Repository:
- Ecological Society of America
- Date Published:
- Journal Name:
- Ecosphere
- Volume:
- 17
- Issue:
- 5
- ISSN:
- 2150-8925
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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