Changes in a bumblebee alpine pollinator network over 40 years

Abstract Plant–insect interactions within alpine ecosystems are particularly susceptible to anthropogenic impacts, including climate change. Thus, repeated measures of alpine interaction networks, such as pollination networks, are critical for the ongoing management and conservation of these ecosystems. We repeated a pollination study conducted 40 years prior on the Beartooth Plateau, an alpine environment in the north central Rocky Mountains. Of primary concern were potential changes to plant‐pollinator networks at the study area between 1980 and 1981 and 2021. We found that, over time, (1) changes to the composition of bumblebee ( Bombus ) species within alpine pollinator guilds were complex, with apparent losses/additions of species and abundance changes in others; (2) overall capture rates of pollinators on alpine plants decreased; (3) network analyses showed decreases in nestedness, connectance, linkage density and increases in specialisation; and (4) observed changes in plant flowering phenology were consistent with those of many other ecosystems affected by global warming, with a strong trend of advanced flowering phenophase. Our study provides a baseline for understanding decadal‐level changes to alpine pollination networks during the 20th and 21st centuries and allows new insights into how alpine ecosystems may respond to climate change.