Climate-driven alterations reshape flower coloration and possible plant-pollinator interactions in wet grasslands

Climate change is a global phenomenon that has a significant impact on ecosystems. In this study, we investigated whether extreme climatic events associated with global warming are altering the composition of insect-pollinated plant species and whether this is leading to exacerbated changes resulting from the disruption of plant-pollinator interactions. We conducted an experiment to artificially induce extreme climate conditions, which allowed us to analyse their impact on the flower colour composition of vegetation communities. The experiment was carried out in a wet grassland. We measured flowering phenology and flower colour visual signals of bees and flies (hue, saturation, and brightness) under the influence of simulated changes in environmental conditions. The results showed that additional irrigation and passive warming accelerated the onset of flowering and reduced the number of flowering insect-pollinated species over the growing season. Additional irrigation, increased temperature, and their interaction increased flower saturation of bee and fly visual spaces, and decreased saturation in butterfly visual space colour within the analysed plots. We also found that changes in water availability can lead to selective pressures that favour different flower colour traits, potentially affecting the overall dynamics of pollinator interactions. Additional irrigation reduced the proportion of bee-green and fly-yellow plant species. Warming without additional irrigation increased the proportion of bee-green species, but decreased the proportion of bee-UV-green and fly-UV cover plants. Moreover, the analysed factors and their interaction drive changes in the composition of plant communities that shape hue perception patterns in butterflies. These results highlight the complexity of ecosystem responses to climate-related factors, where multiple interacting variables can lead to unexpected changes in floral traits, such as changes in flower colour saturation of different pollinator groups or shifts in dominant hues, ultimately impacting pollinator behaviour and potentially overall biodiversity. • Simulated climate change affects flowering and visual traits of insect-pollinated plants. • Passive warming caused earlier flowering in insect-pollinated plants on wet grasslands. • Irrigation and warming increased the community-weighted mean of flower saturation. • Passive warming and irrigation influenced the abundance of insect-pollinated plants.