Floral pigmentation is shaped by both biotic and abiotic pressures. UV absorbing pigments serve a dual role in plants, they display visual cues to pollinators and protect reproductive structures from UV radiation and temperature stress. Since climate change could be altering the conditions that determine flower pigmentation, and páramos are one of the most vulnerable ecosystems, we characterized floral UV pigmentation in the páramo’s flora along an elevation gradient of ca. 600 m in Cocuy National Park. We also tested how changes in UV radiation and temperature are related to floral UV pigmentation. We sampled inflorescences of the plant family Asteraceae along the gradient, and by UV photography and spectrophotometry, we determined the UV pigmentation patterns and UV-absorbing pigment concentrations. Additionally, we also measured UV irradiance and temperature along the gradient and determined that the highest elevations have lower temperatures and higher UV irradiance. Most of the species have contrasting reproductive structures with UV-absorbing disc florets and UV-reflective pollen, which acts as a visual cue to pollinators. The UV-absorbing pigments of species with inflorescences facing the sun (from the genera Monticalia, Baccharis, Werneria) were significantly affected by elevation, while species with inflorescences that do not receive direct radiation were not significantly affected by elevation (Culcitium and Espeletia). In addition, species that do not change UV pigment concentrations may prioritize pollination against abiotic stress, while species that change pigment concentrations prioritize protection from abiotic stress. This is the first study to characterize UV pigmentation in the páramo’s flora.
