Climate warming changes synchrony of plants and pollinators

Climate warming changes the phenology of many species. When interacting organisms respond differently, climate change may disrupt their interactions and affect the stability of ecosystems. Here, we used GBIF occurrence records to examine phenology trends in plants and their associated insect pollinators in Germany since the 1960s. We found strong phenological advances in plants, but differences in the extent of shifts among pollinator groups. The temporal trends in plant and insect phenologies were generally associated with interannual temperature variation, and thus likely driven by climate change. The phenological advancement of plants did not depend on their level of pollinator dependence. When examining the temporal co-occurrence of plant-pollinator pairs from 1980 onwards, the temporal trends in their synchrony again depended on the pollinator group: while the synchrony of plant-butterfly interactions remained unchanged, interactions with bees and hoverflies tended to become more synchronized, mainly because the phenology of plants responded more strongly to climate change and plants caught up with these pollinators. If the observed trends continue, these interactions are expected to become more asynchronous again in the future. Our study demonstrates that climate change affects the phenologies of interacting groups of organisms, and that it also influences their synchrony.