UV pigments of red bird-pollinated flowers attract birds and deter bees

Authors

• Melissa León-Osper
• José C. Del Valle
• M. Luisa Buide
• Montserrat Arista
• Pedro L. Ortiz
• Amelia A. Fuller, Santa Clara UniversityFollow
• Katie Conrad
• Victor Rossi
• Justen B. Whittall, Santa Clara UniversityFollow
• Eduardo Narbona

Document Type

Article

Publication Date

1-19-2026

Publisher

Elsevier

Abstract

Traits that shape ecological interactions and confer assortative mating can lead to reproductive barriers and, in some cases, drive speciation.1,2 Understanding their role in nature is key to explaining the origins and maintenance of biodiversity. Red flowers in hummingbird-pollinated plants shape ecological performance through pollinator interactions and influence mating by conferring reproductive isolation via pollinator shifts.3,4 The evolution of red coloration in hummingbird-pollinated flowers has been attributed to mechanisms that deter bees or enhance bird attraction.5,6 However, the ecological and evolutionary significance of UV floral pigmentation—visible to both hummingbirds and bees—remains largely unexplored. We compared red-flowered species from western North America (California) and southern Spain that are primarily pollinated by hummingbirds and bees. We found that most red bird-pollinated species in California exhibited chromatic contrast values below bee discrimination thresholds, consistent with the bee-avoidance hypothesis. Conversely, in the hummingbird visual system, these species showed 1.5 times higher chromatic contrast than red and non-red bee-pollinated species from Spain and California, respectively, supporting the bird-preference hypothesis as well, which would promote pollinator-mediated isolation. Bird-pollinated red flowers contained 5 times more UV-absorbing pigments than red bee-pollinated species from California and Spain, whereas the anthocyanin levels were similar. By simultaneously enhancing pollinator attraction, deterring less efficient visitors, and providing ecophysiological benefits, UV-absorbing pigments may be key targets of selection by these pollinators and non-pollinator agents alike and represent a potential “magic trait” in the evolution of red flowers in bird-pollinated species.

Recommended Citation

León-Osper, M., Del Valle, J. C., Buide, M. L., Arista, M., Ortiz, P. L., Fuller, A. A., Conrad, K., Rossi, V., Whittall, J. B., & Narbona, E. (2026). UV pigments of red bird-pollinated flowers attract birds and deter bees. Current Biology, 36(2), 532-540.e4. https://doi.org/10.1016/j.cub.2025.11.054